Molded wood fiber web and structural panels made utilizing the fiber web

A molded structural-wood-fiber product is disclosed that is formed in three dimensions under conditions of heat and pressure. The molded product has the form of a single-piece wood-fiber web consisting of corrugations having indentations along the ridges of the corrugations on both sides of the web. Sheet facings may be applied to one or both sides of the fiber web to form a stiff, lightweight composite panel that has similar stiffness both along and across the corrugations. Several fiber webs or composite panels may be bonded together in stacked configurations to produce high-strength, light-weight panels, beams or platforms for heavy-duty applications. The unique structure of the three-dimensional fiber web permits straightforward high-speed manufacture using a rigid mold and one-dimensional pressing forces. Specific items that can be manufactured utilizing the fiber web and composite panels include pallets, bulk bins, heavy-duty boxes, shipping containers, wall panels, roof panels, cement forms, partitions, poster displays, reels, furniture, caskets, and doors.

FIELD OF THE INVENTION 
This invention relates generally to the production of structural-fiberboard 
products, and particularly to articles of manufacture comprising 
three-dimensionally molded wood-fiber structures that are utilized in the 
construction of composite structural-fiberboard panels. 
BACKGROUND OF THE INVENTION 
A wide variety of forest products are manufactured from wood fibers. The 
present invention focuses upon a class of wood-fiber products that are 
molded in three dimensions under conditions of heat and pressure to 
produce a structural wood fiber web that serves as the principal 
structural component of composite structural-fiberboard panels. The 
geometry of the web of the present invention permits the use of 
straightforward mass-production techniques, utilizing a simple rigid mold 
that may be pressed together with one-dimensional forces. When the fiber 
web is bonded to sheet coverings or facings to produce a composite panel 
product, the composite structure forms a strong, lightweight, rigid 
three-dimensional truss. The prior art does not disclose a wood-fiber 
structure of the form of the invention nor does the prior art show 
fiberboard structures having three-dimensional features that may be so 
readily mass-produced in a wide range of overall board thickness. 
In the prior art, methods and apparatus are disclosed for forming various 
other fiberboard products having three-dimensional elements. For example, 
Setterholm and Hunt in U.S. Pat. No. 4,702,870 describe a method and 
apparatus for forming three-dimensional structural components from wood 
fiber. Their method and apparatus require the use of a resilient mold 
insert to form three-dimensional features in the finished fiberboard 
product. The resilient mold insert is most commonly composed of an array 
of elastomeric protuberances. The elastomers are attached to a rigid 
support plate. 
Elastomers are weak and difficult to attach firmly to the support plate. In 
mass-production of wood-fiber products, elastomeric mold elements exhibit 
problems with compression-set and relatively rapid deterioration under the 
heat and pressure necessary for product consolidation and drying. As a 
result, the elastomeric mold elements have a relatively short lifetime and 
need to be frequently replaced in high-speed production facilities. In 
addition to short mold lifetimes, the three-dimensional fiberboard objects 
disclosed in the invention of Setterholm and Hunt are limited to objects 
having a flat face, backed by webs extending approximately normal to the 
flat face. 
Heat transfer from the resilient mold insert of Setterholm and Hunt to the 
fiber mat is slow because of the low thermal conductivity of the 
elastomeric elements of the mold inert and because of long 
thermal-conduction pathways to regions of the fiber between the 
elastomeric mold elements. Slow heat transfer results in long drying times 
within the press, a major problem for this method, particularly for thick 
products. Drying speed may be increased using radiowave heating of the 
fiber mat, but this increases the complexity and cost of equipment used to 
form and dry the fiberboard products. 
Thus, the invention of Setterholm and Hunt reveals the structure of a very 
specific wood fiber product that is formed using a method and an apparatus 
that are not readily adapted to high-speed mass-production, particularly 
in the case of thick panel products. As will become apparent in the next 
several sections, the present invention defines a new fiber structure that 
may be used in many of the same applications as the invention of 
Setterholm and Hunt, yet without the drawbacks in product formation and 
mass-production encountered with the invention of Setterholm and Hunt. 
A process for making grids from fibers, described by Hunt in U.S. Pat. No. 
5,277,854, also uses the idea of a resilient mold insert which is capable 
of forming objects in three-dimensions. Because of the use of a resilient 
mold insert, this invention suffers from the same difficulties as does the 
invention of Setterholm and Hunt. In addition, while the mold insert of 
Hunt is capable of generating three-dimensional forces, it is used to 
generate a fiber product that has generally two-dimensional features only. 
In U.S. Pat. Nos. 5,198,236 and 5,314,654, Gunderson and Gleisner describe 
a method and apparatus that uses a rigid mold to form three-dimensional 
features in structural fiberboard products. Once again, the fiberboard 
products disclosed in their patent are limited to flat-faced objects 
backed by webs extending approximately normal to the flat face. In 
addition, the rigid mold elements disclosed by Gunderson and Gleisner must 
be retracted during consolidation of the fiber. In U.S. Pat. No. 
5,314,654, a second forming step is required using a resilient mold insert 
similar to that of Setterholm and Hunt. Therefore, formation of the 
structural fiberboard product disclosed by Gunderson and Gleisner suffers 
from the same difficulties as have been pointed out for the invention of 
Setterholm and Hunt. In addition, the need for retractable mold elements 
makes this method complex and expensive. 
Prior art disclosed in U.S. Pat. No. 5,316,828, by Miller, reveals a 
reinforced fluted medium and corrugated fiberboard that has increased 
strength and stiffness in comparison to conventional corrugated fiberboard 
due to the addition of three-dimensional elements in a simple corrugated 
fiberboard structure. The three-dimensional elements take the form of 
adhesive material applied along lines that are transverse to the flutes. 
The adhesive at least partially fills in and bridges across the valleys of 
the flutes, holding the corrugated board more rigid under compressive and 
bending stresses both along the corrugations and across the corrugations. 
The invention requires two distinct materials, wood fiber and adhesive, to 
form the basic structure of the product. The structure of Miller is 
therefore not formed as a single piece and would require multiple 
manufacturing steps. In addition, considerable adhesive would be required 
to fill in the valleys to the top of the flutes. The adhesive could fill 
in and bridge only a small portion of the flutes in thick corrugated 
boards, making the technique ineffective for thick corrugated panels. 
Finally, application of adhesive to both sides of the fluted medium would 
increase product weight and material cost, and complicate board 
manufacture. 
In U.S. Pat. No. 4,726,863, Cline describes a method for making a 
high-strength composite paperboard panel. The panel is composed of an 
undulated midstratum layer to which are adhesively bonded an underlayer 
and an overlayer. There is no variation of the structure along the flutes 
formed by the undulations, making the structure generally two-dimensional 
and placing it in a different structural class than the present invention. 
Because of its two-dimensional structure, which is similar to the 
structure of conventional corrugated boards, the panel product disclosed 
by Cline has less strength and stiffness across the undulations compared 
to along the undulations. 
In summary, numerous composite wood-fiber panel products are described in 
the prior art. Only a few of these products are comprised of 
three-dimensional elements which produce fiberboard panels having high 
strength-to-weight ratios and approximately equal strength and stiffness 
in all directions within the plane of the panels. The prior art 
disclosures of three-dimensional elements in fiberboard panels all suffer 
from significant difficulties in production of thick panels and in 
mass-production at high-speeds. These difficulties have impeded 
implementation of much of the prior art by the fiberboard industry and 
end-users. The present invention overcomes these difficulties by defining 
a new three-dimensional wood-fiber structure that has excellent 
strength-to-weight properties, and yet it can be readily mass-produced in 
the form of both thin and thick panels. 
SUMMARY OF THE INVENTION 
The invention consists of an article of manufacture having the form of a 
three-dimensional wood-fiber web that can be produced using a simple rigid 
mold pressed together with one-dimensional pressing forces. The web serves 
as a basic structural component for numerous panel products. Examples 
presented in this disclosure focus upon fiber webs made using a 
wet-forming process in which the wood fiber is prepared by mixing the 
fiber with water, thereby forming a slurry. It is to be understood that 
other fiber preparations are possible, including dry-forming preparations 
in which adhesive binders are added to relatively dry wood fiber. These 
other preparations will present themselves to those skilled in these arts. 
The fiber web is formed as one piece under heat and pressure after most of 
the carrier fluid is drained or squeezed from the slurry as the rigid mold 
is pressed together. Once formed using the rigid mold, the fiber web 
contains corrugations that have syncline (V-shaped) indentations along the 
ridges of the corrugations on both sides of the web at spaced positions 
along the ridges of the corrugations. The opposite surface of the 
indentations form anticline (inverted V shaped) protrusions that function 
as corrugation stiffeners bridging across furrows of the corrugations. 
These elements produce sloped web surfaces. The valleys and ridges of 
these elements may be flat. Flat ridges provide an exterior surface for 
the application of adhesives that bond the web to additional components. 
Surfaces that are either sloping or flat allow formation of the web using 
a simple rigid mold that is pressed together using a one-dimensional 
pressing force. 
In structural panel applications, sheets of material are adhesively bonded 
to the flat ridges of the shaped web on one or both sides of the web, 
providing smooth facings which cover the web. The web thereby serves as a 
stiff, light-weight structural core which is sandwiched between sheet 
facings to form a composite panel. The sheet facings may be composed of a 
variety of materials including pressed fiberboard, wood veneers, metal, 
plastic, and the like. The combined structure, consisting of the 
three-dimensional web bonded to sheet material, forms a three-dimensional 
rigid truss that has a high strength-to weight ratio, and produces nearly 
equal strength and stiffness in all directions within planes that are 
parallel to the facings. 
Numerous other structures are possible by combining elements of the 
invention in various ways. For example, individual shaped webs may be 
joined in stacked arrays to increase strength and stiffness. Sheet 
materials can be joined to the ridges of the exterior webs of these 
stacked arrays to form stiff but lightweight platforms, panels, or beams 
having smooth exterior surfaces. Sheet materials may also be bonded 
between each web in stacked configurations to simplify adhesive attachment 
of the various layers and increase product strength and stiffness. The 
edges of stacked arrays may be used as the load bearing elements in some 
applications where very high stiffness and compression resistance are 
required. 
The various embodiments of the invention have applications in a wide range 
of industries including packaging, material handling, construction, and 
furniture industries. A few of the specific products that can be fashioned 
using the invention include pallets, bulk bins, heavy duty boxes, shipping 
containers, wall panels, roof panels, cement forms, partitions, poster 
displays, reels, desks, caskets, shelves, tables, and doors. 
ADVANTAGES OF THE INVENTION 
Unlike the prior art, the present invention discloses a three-dimensional 
fiber-web structure that can be readily produced to any practical size as 
a single piece under heat and pressure using rigid molds that are pressed 
together in one direction. The molded fiber web can be easily bonded to a 
variety of sheet materials or to other webs to form numerous rigid 
structural fiberboard panels that have high strength-to weight ratios 
relative to solid panels having comparable overall dimensions. In one of 
the preferred embodiments, the three-dimensional features of the web 
impart nearly equal strength and stiffness in all directions within the 
general plane of the panels. 
In production of the fiber web, many types of wood fibers and combinations 
of wood fibers may be utilized ranging from 100 percent softwood fiber to 
100 percent hardwood fibers, including all of the various combinations of 
mixed hardwood and softwood fiber. Hardwood fibers are normally difficult 
to work with, but by holding the fiber mass together under heat and 
pressure as the fiber web dries, strong fiber bonds are formed even for 
hardwood fibers. 
Strong fiber bonds can be formed using the aforementioned press-drying 
procedure without the need for additive binders. The absence of additive 
binders allows the fiber webs to be readily recycled. In many 
applications, discarded products made in accordance with the present 
invention can be recycled along with other common corrugated containers. 
The fibers, either hardwood or softwood, can be derived from any sort of 
secondary quality raw material source such as small trees, misformed 
trees, limbs, underutilized wood species, recycled paper and cardboard. 
This is an important advantage with regard to efficient utilization of 
forest resources. 
The sheet facings bonded to the web may be composed of a variety of sheet 
materials including wood veneers, fiberboard, plastics and metals. Because 
the sheet facings are produced separately from the structural web, the 
physical properties of the web may be controlled independent of the 
physical properties of the sheet facing. Independent control enhances the 
versatility of the invention. For example, density of the web may be 
adjusted relative to the density of any fiber sheet facing so that 
strength of each element may be matched to achieve optimum 
strength-to-weight ratios. 
In the invention of Setterholm and Hunt, density of the structural-support 
web relative to the density of the facing was more difficult to control, 
since the forces forming the support web were not independent of the 
forces forming the facing. In early tests of thick products, the density 
of the support web was found to be much lower than the density of the 
facing, leading to poor crush resistance relative to product basis weight. 
The particular geometry of the present invention is designed to permit the 
use of a simple rigid mold which is part of a relatively simple, 
highly-reliable molding system. The mold elements do not need to be 
retracted during formation, as in the prior art. Since the mold elements 
are rigid they can be composed of various metals, such as stainless steel 
or aluminum. They may even be composed of any of a variety of common 
high-strength, high-temperature, durable non-metals, such as aluminum 
oxide. In some applications, various plastics or plastics reinforced with 
fillers may be used. 
Unlike the prior art, mold elements utilized to produce the present 
invention can be firmly and reliably attached to support members using 
straightforward mechanical attachments, or through welding or brazing if 
the mold elements are metallic. In many cases, mold elements may be 
readily machined directly into a mold support plate, forming a very 
strong, durable one-piece mold plate. Relative to the resilient mold 
insert disclosed in the prior art, the rigid mold of the present invention 
will have a very long life expectancy. It will offer trouble-free 
performance in production applications, minimizing machine maintenance 
requirements and downtime. 
The sloped surfaces and flat valleys and ridges of the fiber web permit the 
application of three-dimensional forming forces using a rigid mold that is 
pressed together in one direction. In addition to vertical forces 
developed as the mold plates are pressed together, lateral forces result 
from the outward swaging that occurs as the sloped surfaces of the molds 
are pressed together. This aspect of the invention has an enormous 
advantage since it is straightforward to make molds that are pressed 
together in one direction. Experimentation has confirmed that mold surface 
angles may be found that produce uniform, high-density webs. 
Experimentation has also determined that the webs have excellent release 
properties upon separation of the molds. Prior art required a resilient 
mold insert in order to produce three-dimensional forming forces from a 
one-dimensional pressing force. 
As mentioned previously, the rigid mold of the present invention can be 
metallic. A metallic mold may be actively and effectively heated with 
common heating sources such as steam, electric or gas heat. The metallic 
mold surfaces are in close contact with every surface of the web during 
web formation. Very rapid and efficient heat transfer from actively heated 
metallic molds to all regions of the fiber web will therefore occur. The 
web can thereby be rapidly dried and/or bonding agents rapidly cured as 
the web is pressed and heated simultaneously. High product throughputs are 
then possible. Relatively inexpensive sources of heat may be used and 
means for actively heating the molds readily applied. 
In the prior art, heat transfer rates across elastomeric mold elements were 
slow due to the low thermal conductivity of elastomers. In addition, heat 
conduction paths from heated metal surfaces of the mold to regions of the 
fiber between elastomeric mold elements were relatively long, particularly 
for thick products. Long heat conduction distances contributed to slow 
heat transfer rates. In this circumstance, rapid fiber-drying rates and 
high product throughput could be achieved only through the implementation 
of costly techniques such as radiowave heating or parallel processing. 
Only thin panels could be efficiently mass-produced because of the slow 
heat transfer rates and associated slow drying rates of thick fiber-panel 
products. 
Production of the fiber webs disclosed herein may be accomplished in a 
variety of ways. Webs can be formed one at a time in batch operations 
using a single mold in a single opening press. Several webs may be 
produced simultaneously using several molds arranged in a stacked 
configuration in a multi-opening press. The webs can also be formed 
continuously using moving molds on continuous belted presses or 
counter-rotating roller presses, or the like. It is to be understood that 
other production techniques will present themselves to those skilled in 
the art. In addition, while the focus of the present invention is upon 
formation of fiber webs that use a fluid carrier to mix and deposit the 
fibers in the mold, the invention also applies to the formation of fiber 
webs using adhesive-coated dry-fiber furnish, as mentioned previously.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1-3 illustrate one embodiment of the invention. Perspective 
renderings of different views of the embodiment are shown in these first 
three figures to clarify the basic structure of the invention. The 
structure depicted in FIG. 1 shows an upper surface view of the 
pressed-fiber web consisting of a series of undulations or corrugations 1 
along which are numerous V-shaped openings (referred to hereinafter as 
syncline indentations 4) downward into the ridges of the corrugations and 
other numerous inverted-V-shaped protuberances (referred to hereinafter as 
anticline protrusions 5) upward from the valleys of the corrugations. The 
anticline protrusions 5 may have the same height as the corrugations, as 
shown in FIG. 1, or they may be set back from the ridges of the 
corrugations. 
The direction of the axes of the corrugations are indicated by the arrows 3 
in FIG. 1, for reference. For webs that are formed about a plane, the 
midplane of the web may be defined as a horizontal plane which passes 
through the middle of the structure in the narrow overall height 
dimension. The midplane is generally normal to the direction in which 
force is applied to form the web. 
The direction of the valleys of the syncline indentations 4 and the ridges 
of the anticline protrusions 5 are approximately normal to the axes of the 
corrugations in the figures. Other relative angles may be used if desired. 
The anticline protrusions 5 are formed by indenting the valleys of the 
corrugations from the underside of the structure shown in FIG. 1. In this 
sense, both the syncline indentations 4 and the anticline protrusions 5 
are indentations into corrugation ridges made in the same fashion but from 
opposite sides of the fiber web structure. 
The walls formed by the syncline indentations 4 and anticline protrusions 5 
span or bridge the space between adjacent walls of the corrugations. By 
bridging this space, the syncline indentations 4 and anticline protrusions 
5 act as a type of gusset or stiffener for the corrugations 1. They also 
provide strength and stiffness in directions normal to the axes of the 
corrugations. A fiber web fashioned in this manner holds its as-molded 
form without the need for additional support. The self-supporting feature 
of the fiber web in the present invention makes assembly into stacked 
configurations very simple and convenient. The self-supporting feature 
also allows the invention to be used in the as-molded condition, which 
would be useful in some packaging applications. 
The peaks or ridges 6 of the structure on both the top and bottom surfaces 
of the web may be flat. These flat features along the ridges form surfaces 
that are convenient and effective sites for the application of adhesives 
used to bond the structure to various types of sheet coverings or facings, 
or to bond several webs together to form stacked configurations. As 
depicted in FIG. 1, these flat-topped ridges may consist of peaks or 
ridges of the anticline protrusions 5 in addition to peaks or ridges of 
the corrugations 1. 
FIG. 2 provides another perspective drawing of the first embodiment. In 
this case, the structure shown in FIG. 1 has been sectioned along plane 
2--2 in FIG. 1 to reveal some of the features of the cross-section and the 
underside of the structure. FIG. 3 is another perspective drawing showing 
a single corrugation that has been split apart at a plane through the 
middle of the corrugation. The formation of the anticline protrusions 5 by 
indentation of the valleys of the corrugations is clarified by this 
rendering of the structure as well as the rendering shown in FIG. 2. It is 
clear from FIGS. 2 and 3 that the structure is a relatively thin 
three-dimensional web having sloping surfaces and flat ridges. 
The topology of the structure of the present invention permits formation of 
the three-dimensional web as a single continuous piece in a single molding 
operation using a simple rigid mold that is pressed together with 
one-dimensional forming forces. The top and bottom mold surfaces used to 
form the present invention contain negative impressions of the top and 
bottom surfaces, respectively, of the structure. Unidirectional mold 
pressure is applied in a direction generally normal to the planar axis or 
midplane of the web structure. 
The ability to form the fiber web as a single piece in a single molding 
step using a rigid mold can be understood in mathematical terms that 
characterize the web surfaces as single-valued functions of coordinates of 
the midplane of the structure. No part of the web is therefore intersected 
more than once as the mold moves towards the web in its finished form. In 
simpler terms, no part of the web folds back on itself or has hollow 
regions, which would otherwise make rigid mold access impossible in a 
single molding step to form a single continuous web. 
Just as the angled or sloped surfaces of the web permit ready formation of 
the three-dimensional web structure, they also permit ready separation of 
the mold from the web after formation of the web. Experiments to be 
described later have demonstrated excellent mold-release properties, 
confirming this advantage. In the prior art, formation of 
three-dimensional features required fragile and expensive elastomeric 
molds or the use of multiple components or materials, and multiple 
manufacturing steps, as has already been described. 
The fiber furnish, from which the fiber web is formed, can be prepared a 
number of different ways. For example, the furnish can be prepared from a 
mixture of wood fiber and a carrier fluid, such as water. Agitation of the 
mixture produces a slurry having a reasonably uniform distribution of wood 
fiber. Usually, the carrier fluid makes up most of the slurry. The 
agitated slurry is poured into a deckle which encloses the mold. The 
carrier fluid is drained through porous openings in the molds and is 
driven out by gravity forces and differential pressure applied to the 
molds. 
After most of the water is removed from the slurry through drainage and 
compaction, heat is applied to the web through thermal conduction from 
heated mold surfaces in order to remove the remaining water and dry the 
web under pressure. Radiowave energy may also be applied to the web in 
order to heat the web and increase drying speed. For thin fiber webs, 
however, increases in drying speed produced with radiowave heating may be 
only marginal. This is because heat from the mold surfaces is already 
rapidly transferred throughout the volume of the fiber web, due to the 
short heat conduction paths in thin webs. 
FIG. 4A shows a top view of a three-dimensional fiber web that is similar 
to the web depicted in FIGS. 1 and 2. In this case, a little larger web is 
shown having more indentations and protrusions. The top view shows a 
skewed shape intentionally, in order to clarify the web structure or 
pattern. The web can be made to have a rectangular perimeter or any other 
perimeter shape by trimming the edges or forming the web with the desired 
perimeter shape. 
In FIG. 4A, the flat-topped ridges 7 of the structure are represented by 
the heavy black lines in the top view, while the flat-bottomed valleys 8 
are represented by the hatched pattern in the top view. As already 
mentioned in connection with FIGS. 1-3, the flat portion of the ridges 7 
forms an excellent surface for applying adhesive used to bond the web to 
facings or other fiber webs. The thin angled lines in the top view are the 
edges of syncline indentations into the paper and anticline protrusions 
out of the paper. Thus, the diamond shaped elements in FIG. 4 containing 
hatched horizontal lines represent syncline indentations 9, while those 
containing heavy solid lines represent anticline protrusions 10. 
FIG. 4B shows a lower-edge view of the structure depicted in FIG. 4A. The 
view presented in FIG. 4B is indicated by cross section 4B--4B in FIG. 4A. 
An end view of the corrugations 11 and the sides of the anticline 
protrusions 10 are visible in this view of the invention. FIG. 4C shows a 
right edge view of the web showing yet another view of the syncline 
indentations 9 and anticline protrusions 10. The right edge view in FIG. 
4C is indicated by cross section 4C--4C in FIG. 4A. 
In the embodiment depicted in FIG. 4, the positions of the syncline 
indentations 9 and the anticline protrusions 10 are staggered along 
adjacent corrugations. By staggering these elements, bending strength and 
stiffness may be imparted to the structure both along the corrugations and 
across the corrugations. 
FIG. 5A is a top view of a web in which syncline indentations 12 and 
anticline protrusions 13 are lined up in a direction normal to the 
corrugations to facilitate bending or folding of the web across the 
corrugations. A lower edge view of this embodiment is shown in FIG. 5B and 
a right edge view is shown in FIG. 5C. The topology of this particular 
embodiment of the invention permits the use of molds that can be readily 
machined on three-axis milling machines from a single piece of rigid 
material. Somewhat greater distances are shown between the indentations 
and protrusions in FIG. 5, compared to FIG. 4, to illustrate the fact that 
the spacing and position of the syncline indentations 12 and anticline 
protrusions 13 can be varied. The appropriate positions and spacing will 
be determined by product application requirements such as strength across 
the corrugations, economics of mold fabrication, final product shape, and 
end use. 
The ability to fold or bend the web is an advantage in numerous 
applications. For example, in the manufacture of boxes, the web may be 
folded at the corners and subsequently covered with a facing to produce a 
smooth surface. Box assembly in this sequence is greatly facilitated by 
the fact that the webs are self-supporting in the as-molded condition. 
Either stiff sheet materials, such as wood, metal and hard plastics, or 
more flexible sheet materials, such as thin fiberboard or paperboard, may 
be applied to the web to form the box surface in this case. Using a 
different assembly sequence, folding may be performed after the facing is 
applied to the web, as is done in conventional corrugated board 
manufacture. In this case, the facing must be flexible in order to allow 
the facing to be creased along the fold line prior to bending. 
It is also possible to form a fiber web composed of staggered indentations 
and protrusions over most of the area of the web except along 
predetermined fold lines. Along these fold lines, the indentations and 
protrusions would be lined up. Using a combination of linear and staggered 
web features, readily folded panels may be produced that are rigid both 
along the corrugations and across the corrugations. Panels assembled from 
the webs may be subsequently folded or shaped in various predetermined 
ways to produce a wide variety of products. 
FIG. 6 illustrates an example of smooth, flat-surface sheets 17 that may be 
bonded to the ridges 18 of the fiber web 19. In this example, a web 19 
like that illustrated in FIG. 5 is drawn. The composite structure becomes 
a flat surface panel with a fiber web 19 backing or core. The sheet 
material 17 applied to the web 19, spans the gap across the tops of the 
syncline indentations 12, forming a rigid three-dimensional truss. The 
three-dimensional truss formed in this way imparts considerable stiffness 
to the composite panel. 
The smooth surface sheets 17 applied to the web provide excellent surfaces 
for printing and displaying text and graphics, useful for conveying 
information and advertising. Printing may be performed either before or 
after the sheets are joined to the web. While shown as a generally flat 
panel in FIG. 5, curved shapes are also readily produced by forming or 
bending the web 19 in an arc and bonding flexible sheets to the web 19 so 
that the sheets follow the curvature of the fiber web 19. 
For any of the embodiments of the fiber web, many different materials may 
be used in the sheet facing. For example, the facings may consist of wood 
veneers, sheets of wood-fiber-based material, wood-based-particle panel 
materials, plastic or metal sheets. Other sheet materials will present 
themselves to those skilled in these arts. 
FIG. 7A is a top view of an embodiment in which several individual fiber 
webs 19 are bonded together in a stacked configuration. FIG. 7B is a 
bottom edge view of the stack of webs and FIG. 7C is a right edge view of 
the stacked web. The webs 19 may be readily bonded along the surfaces 
formed at the ridges 14 of the individual webs 19. By staggering the webs 
19 as shown in the edge view of FIG. 7B, the gaps at the top of the 
syncline indentations 12 are bridged by stiff portions of the ridges 14 of 
adjacent webs 19. In this way, the structure becomes a complex rigid 
three-dimensional truss having considerable stiffness in all directions. 
Stiffness is attained in this case without the use of sheet facings. 
Even webs made with indentations that are lined up, as in FIG. 5, may be 
made stiff in all directions, including across the fold-line of the 
indentations, by stacking the webs. This is because the stiff bridges 
formed across the gaps of the indentations in properly stacked 
configurations, resist closure of the indentations under bending forces. 
Thus, the simplifications produced by lining up the indentations in the 
webs, discussed in conjunction with FIG. 5, may be realized, yet stiffness 
is maintained both along and across the corrugations in these stacked 
configurations. 
For a given panel thickness, stacked-web embodiments of the invention 
generally have better thermal insulating properties than do panels 
consisting of only a single large web. This advantage is due primarily to 
the separation or partitioning of air spaces through the thickness of the 
stacked web. By partitioning the air spaces, circulating air currents are 
broken up and isolated from each other. Heat transfer through the 
thickness of the stacked web due to heat convection along these air 
currents is thereby minimized. 
While not shown in FIG. 7, sheets of material may also be applied between 
webs 19 within the stack of webs. This additional layering of sheet 
material imparts additional strength and stiffness to the composite panel 
and increased convective heat-transfer resistance across the panel. 
Increased convective heat-transfer resistance results from further 
separation and partitioning of the air spaces within the stacked web in 
these embodiments. 
As an additional benefit of adding sheet materials between the webs 19 in 
stacked configurations, adhesive bonding of the various layers is 
simplified. This advantage arises because the sheets provide broad bonding 
surfaces. In this circumstance, adjacent layers of the stack do not need 
to be positioned as accurately as is necessary without the sheet layers. 
Without the sheet layers, web ridges, 7 and 14, must be carefully aligned 
before they are bonded. 
FIG. 8 depicts the application of sheet facings 17 to the ridges 14 of 
exterior webs of the stacked configuration, to give the stack greater 
stiffness and a smooth surface. Once again, sheets may or may not be 
placed between webs 19 within the stack, depending upon the application. 
FIG. 9 shows an embodiment in which numerous webs 19 are stacked 
horizontally. In this case, sheet facings are applied to the edges of the 
stack rather than to the exterior web ridges 14. For this configuration, 
individual webs would typically have a narrow width (height dimension in 
FIG. 9) relative to web overall length (dimension into the paper in FIG. 
9). The stacked web and sheet facings depicted in FIG. 9 would be useful 
in the formation of relatively thick beams and platforms in which heavy 
loads are applied to the edges of the webs 19. In addition, sheet 
coverings along the edge of stacked panels would keep debris from entering 
the stack of webs. 
Once again, sheet materials may be placed between webs within the stack 
shown in FIG. 9 to impart additional strength and stiffness to the 
composite structure. While not shown in FIG, 9, sheet facings may also be 
readily applied to the edges of the composite panel at the right, left and 
facing views of the structure depicted in FIG. 9. With the addition of 
these sheet facings, the composite panel would be completely enclosed on 
all sides by smooth facings. 
It is also possible to nest the fiber webs. By bonding multiple webs 
together in nested configurations, the strength and stiffness of the webs 
can be substantially increased compared to the strength and stiffness of a 
single web. Nesting permits web thickness, strength and stiffness to be 
varied over a wide range using only a single web configuration and a 
single forming apparatus. 
The invention in its various forms can be used to make a wide variety of 
structural products in packaging, material handling, construction and 
furniture industries. Products include pallets, bulk bins, heavy duty 
boxes, shipping containers, wall panels, roof panels, cement forms, 
partitions, poster displays, reels, desks, caskets, shelves, tables, and 
doors. Other applications will present themselves to those skilled in the 
art. 
The invention can be formed from wood fibers of all types. It can be formed 
with wood fiber alone, containing no chemical additives, making products 
easily recyclable. It can also be formed with resin or binder additives to 
enhance properties, although these products may not be recyclable. The 
invention can also include various other additives and treatments to 
impart specific properties to the structure such as resistance to water, 
fire, and insects. Other additives and treatments will present themselves 
to those skilled in the art. 
An experiment was conducted during the development of the invention to 
determine the viability of forming a fiber web of the type disclosed 
herein using a solid mold and a one-dimensional pressing force. For these 
experiments a fiber web having staggered syncline indentations and 
anticline protrusions, similar to the web depicted in FIGS. 1-4, was 
fabricated. Other experimental parameters are listed below: 
1. The corrugation and indentation surfaces sloped at angles of 45 degrees 
with respect to the midplane of the web. 
2. The perimeter of the web was rectangular, with overall dimensions 12.5 
cm.times.10 cm.times.1 cm. 
3. The web consisted of five adjacent corrugation sections, each section 
having a form similar to that shown in FIG. 3. 
4. Each corrugation section contained either 2 or 3 syncline indentations 
and 2 or 3 anticline protrusions along the length of the corrugation 
section. 
5. The ridges of the web were flat with a width of 0.18 cm. 
6. The rigid mold plates were fabricated from aluminum. 
7. A series of small holes were placed along the valleys of the pattern in 
the mold plates to permit removal of water and venting of steam during 
drying. 
8. Fibers were derived from macerated corrugated boxes. A ratio of 
approximately 1 part fiber to 100 parts water, by weight, was utilized in 
the maceration process. 
9. Pressures of approximately 200 PSI were applied to the mold plates 
during formation and drying of the fiber webs. 
10. Mold surface temperatures during drying reached approximately 325 
degrees F. 
11. Final web densities were 900-1000 kilograms per cubic meter. 
In the experiments, the fiber webs were formed and dried in the same mold 
apparatus without removing the webs until they had dried completely. After 
the webs were dry, they released quite readily from the mold surfaces as 
the mold plates were separated. The web surfaces were smooth and web 
features were formed to high accuracy. There was no warping, twisting, or 
other distortion of the web after removal from the mold. Some of the webs 
were subsequently bonded to either paperboard sheets or wood veneer. 
Considerable stiffness and crush strength were obtained in each of these 
composite panels. 
It is to be understood that the structure of the invention differs 
considerably from the structure of conventional corrugated boards. The 
invention relates to structural elements of a particular three-dimensional 
category. By comparison, corrugated boards contain only two-dimensional 
structural elements. Corrugated boards have less strength and stiffness 
across the corrugations compared to along the corrugations. The present 
invention is capable of producing nearly equal strength and stiffness 
along the corrugations and across the corrugations because of the unique 
three-dimensional structure. Simple corrugated medium, without the 
paperboard facing, cannot be readily stacked to form 
efficiently-configured rigid three-dimensional trusses, as is the case 
with the invention disclosed herein. Corrugated medium in common 
corrugated boards are manufactured by corrugating paper sheets, while the 
present invention is manufactured by molding three-dimensional elements 
from a fiber slurry or from dry-fiber furnish mixed with bonding agents. 
Efficiently engineered structures may be produced using the present 
invention because the molding operation and three-dimensional structure 
permit considerable design flexibility. 
Novel and Unobvious Features of the Invention 
The invention is to be distinguished from other inventions disclosing 
structural fiberboard products in that it defines an article of 
manufacture that is a single-piece, three-dimensional fiber web that has 
the form of a series of corrugations 1 with syncline indentations 4 and 
anticline protrusions 5 along the length of the corrugations 1. The 
highpoints or ridges 6 of the web have flat tops to facilitate adhesive 
bonding between webs in stacked configurations and adhesive bonding to 
sheets 17 which act as coverings or facings over the webs. 
The composite structure formed by the fiber web 19 and sheet facings 17 
form a rigid three-dimensional truss that has a high strength-to-weight 
ratio and a high stiffness-to-weight ratio. Increased strength and 
stiffness are produced by stacking several webs in a staggered 
configuration in which the syncline indentations 12 of individual webs 19 
are bridged by the corrugation ridges 14. These stacked configurations may 
also include a variety of sheet facings 17 bonded between webs and to 
exterior webs in order to provide additional strength and stiffness, and 
to give the structure desired surface characteristics. 
The fiber web structure of the present invention has a decided advantage 
over prior art disclosures of three-dimensional structural fiberboard 
products in that the present invention may be molded in a single piece 
using a simple rigid mold pressed together with one-dimensional pressing 
forces. Rigid molds can be made extremely durable for long life in 
demanding mass-production applications. Because of the geometry of the 
invention, the rigid mold is in close contact with every part of the fiber 
web as it is pressed. Thereby, surface heat from the mold is effectively 
transferred to the fiber web, producing rapid drying and requiring less 
press-time than prior art structures. These combined advantages lead to 
greatly simplified fabrication hardware, and reduced costs in 
mass-production. 
In addition, the present invention offers a superior solution to the 
formation of three-dimensional structural fiberboard products, since by 
using a rigid mold to form the fiber web of the present invention, higher 
dimensional precision may be achieved. Higher dimensional precision leads 
to greater strength and makes possible applications requiring close 
tolerances. High precision also makes possible variation of the thickness 
of the web in proportion to the magnitude of anticipated mechanical 
stresses within specific portions of the web. This advantage allows 
optimization of the strength-to-weight ratio of the web and the panels 
made with the web for a particular load and load distribution. 
Precision molding also makes possible accurate formation of rounded or 
filleted features in the corners of the web, such as in the corners where 
the flat valleys 8 meet the sloped surfaces of the web. Rounding or 
filleting of corners will increase resistance to bending and improve 
overall strength of the web or panel. 
Compared to the resilient mold insert described in the prior art, the use 
of a rigid mold to form the present invention permits greater control of 
fiber density and density distribution throughout the fiber web. Improved 
control of fiber density leads to a higher quality, higher strength final 
product. In addition, because the mold can be made of high-strength rigid 
materials, it can be designed to withstand tremendous pressures making 
production of high-density fiberboard products a possibility. 
It is clear that the invention is unobvious since, despite its great 
advantages, the invention has not been implemented nor disclosed by those 
skilled in the art of fiberboard production. Numerous disclosures have 
been made to define methods for the production of other three-dimensional 
structural fiberboard products, but these products have never been 
effectively commercialized because their manufacture has entailed complex 
fabrication procedures and required significant technological 
breakthroughs. 
Manufacture of the invention disclosed herein does not require major new 
technological developments. This advantage, resulting from the unique 
structure of the invention which is conducive to simple and reliable 
manufacturing methods, greatly reduces the start-up risks involved in 
setting up a manufacturing facility. By reducing the technical risks, 
widespread acceptance and application of the disclosed three-dimensional 
structural fiberboard product should occur more readily than has occurred 
with other three-dimensional structural fiberboard products. 
While the invention has been described in detail above, it is to be 
understood that this is by way of example only and the protection granted 
is to be limited solely by the spirit of the invention and the scope of 
the following claims.