Note: Descriptions are shown in the official language in which they were submitted.
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ENVIRONMENTALLY RESISTANT ENCAPSULATED MAT CONSTRUCTION
BACKGROUND
The present invention relates to a reusable system for the construction of
roadways and
equipment support surfaces in areas having poor ground integrity
characteristics. More
particularly, the present invention relates to a system of durable mats which
can be
interconnected to form roadways and/or equipment support surfaces. More
particularly still,
the present invention relates to a reusable system of mats which can be
quickly and easily
positioned in a single layer to form roadways and/or equipment support
surfaces, and which
can thereafter be easily removed and stored until needed again.
Mats for this use are generally known in the art and are available from
Quality Mat
Company, Beaumont, Texas. In remote and unstable environments, a stable
roadway (or any
roadway) often does not exist, such that temporary roadways are assembled by
aligning
planks, boards or mats along the desired path. The mats provide temporary
structures for
various construction projects as well as for use in environmental or disaster
cleanup projects.
These mats enable trucks and other equipment to drive over, store equipment
on, or create
campsites on otherwise unstable, soft or moist land or damaged areas by
providing a relatively
level and stable surface.
While conventional wood mats provide useful service at a reasonable cost, the
wood
core, which is typically made of white oak, can deteriorate over time due to
moisture causing
gradual rotting and degradation of the wood material. This causes the mat to
be discarded,
because unlike some of the other materials that are used on the upper and
lower layers of the
mat, the core cannot be replaced without essentially making an entirely new
mat.
While various mats exist for such uses, there is a need for mats having
improved
resistance to wood deterioration as well as to abuse of and damage to the mats
in order to
extend their service lives. The present invention now provides new mat
constructions that
meet this need.
SUMMARY OF THE INVENTION
The invention relates to an industrial mat comprising a core construction that
provides
strength and rigidity to the mat, and an encapsulation of a thermoplastic,
thermosetting or
elastomeric material or a mixture thereof that surrounds and fully
encapsulates at least each of
the wood components or the entire core construction.
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The core construction comprises a variety of different materials and
components,
including:
(a) plural layers or plies of wood or engineered wood components that are
nailed,
bolted or riveted together to form a rigid core construction, or
(b) a layer or ply of a thermoplastic material in the form of a plurality of
adjacently
arranged elongated members or a sheet member that optionally includes open or
closed cells
therein or therethrough, or
(c) a thermosetting plastic support structure in the form of a plate, beam,
grid, grating,
ladder or pultruded tubes, or
(d) a metal support structure in the form of beams that are welded together to
form a
frame or ladder structure, or a plate that optionally contains apertures
therein, or
(e) at least two layers or plies of elongated, sheet, plate, beam, grid,
grating, ladder or
tube members wherein the layers or plies are fastened or joined together.
The encapsulation has a thickness sufficient to provide environmental
resistance to the
wood components or core construction that it encapsulates, while also
providing abrasion
resistance to the mat. Also, when the entire core structure is encapsulated,
the encapsulation
also forms top and bottom surfaces of the mat.
Advantageously, each layer, ply or support structure has a length and width
that
substantially corresponds to that of the mat and has a thickness of not less
than 0.75 inches
and not more than about 12 inches or between about 1 and about 8 inches or
between about
1.5 and about 4 inches.
The entire core structure may be encapsulated with the top surface, the bottom
surface,
or both the top and bottom surfaces of the mat including a plurality of
channels or grooves to
provide traction to objects moving on the top surface of the mat and/or to
provide resistance to
slipping when the bottom surface of the mat is placed on wet or muddy ground
surfaces.
The core construction is preferably made of materials that provide a load
bearing
capacity that is able to withstand a load of at least 600 to 800 psi without
permanently
deforming the core construction and the encapsulation has a thickness of 0.25
to 1 inch or 0.25
to 0.5 inch.
In various preferred embodiments, the core construction comprises:
- two or three layers or plies of elongated components or members at least
some or all
of which are wood or engineered wood, wherein each layer or ply comprises wood
or
engineered wood in the form of a plurality of adj acently arranged elongated
members or a
sheet member; or
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- one of the layers or plies comprising a structure of a thermoplastic
material in the
form of a plurality of adjacently arranged elongated members or a sheet
member, and another
layer or ply comprising a plurality of adjacently arranged elongated members
or a sheet
member of engineered wood or a thermosetting plastic material; or
- one of the layers or plies comprising one or more elongated components or
members
of metal and another layer or ply comprising a plurality of adjacently
arranged elongated
members or a sheet member of wood or engineered wood; or
- one of the layers or plies comprising a reinforced thermosetting plastic
support
structure in the form of a plate, grid, grating, ladder or pultruded tubes and
another layer or
ply comprising a plurality of adjacently arranged elongated members or a sheet
member of
wood or engineered wood.
The core construction advantageously comprises a central layer made of a
sheet, a
plurality of elongated members, a plurality of compartments, or combinations
thereof and at
least one additional layer positioned adjacent the central layer wherein the
additional layer is
made of a sheet, a plurality of elongated members or combinations thereof.
Furthermore, the
core construction has an upper layer positioned above the central layer
wherein the upper
layer is made of a sheet, a plurality of elongated members or combinations
thereof, and a
lower layer positioned below the central layer wherein the lower layer is made
of a sheet, a
plurality of elongated members, a plurality of compartments, or combinations
thereof.
The core construction typically comprises 2 or 3 layers containing elongated
members
of wood or engineered wood each having a modulus of at least about 1.6 M psi
20%. For
this embodiment, the encapsulation surrounds and fully encapsulates each of
the elongated
wood or elongated wood members of each layer.
Generally, the encapsulation may comprise a thermoplastic, thermosetting or
elastomeric material or a mixture thereof and have a thickness of 0.25 to 1
inch or 0.25 to 0.5
inch. These thicknesses are typically measured from the outer dimension of the
mat although
in some areas when channels or other cutouts are provided the thickness may be
less.
Generally, some thickness is provided so that the core construction is sealed
and not exposed
to water or chemicals that the mat may encounter.
Preferred encapsulation materials comprise polyethylene, polypropylene,
polybutylene
or a thermoplastic polyurethane, a vulcanized rubber material, a polyurethane
material, an
elastomeric material, a mixture of an elastomeric material and a thermosetting
resin such as
crumb rubber particles embedded in a polyurethane matrix. As noted, the core
construction
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provides strength and rigidity to the mat while the encapsulation provides
environmental
resistance to the core construction to which it is applied.
BRIEF DESCRIPTION OF THE DRAWINGS
The appended drawing figures provide additional details of the invention,
wherein:
Figure 1 is an exploded view of the mat of the invention showing the use of
single
width boards for the upper and lower layers, and a core construction that is
encapsulated;
Figure 2 is a view of the assembled mat of Figure 1;
Figure 3 is an exploded view of a mat according to the invention showing the
use of
double width boards for the upper and lower layers, and a core construction
that is
encapsulated,
Figure 4 is a view of the assembled mat of Figure 3;
Figure 5 is a perspective view of a mold that is holding the frame
construction therein
prior to receiving plastic material to form a mat;
Figure 6 is a cross sectional view of the mat after removal from the mold of
Figure 5;
Figure 7 is a view of an encapsulated mat that includes single width boards;
Figure 8 is a view of an encapsulated mat that includes double width boards;
Figure 9 is an exploded view of the mat of the invention showing the use of
single
width boards for the core construction including the central, upper and lower
layers, with the
encapsulation artificially separated into upper and lower portions to
illustrate its position
about the core construction,
Figure 10 is a top perspective view of the mat of Figure 9 as prepared for
use;
Figure 11 is a bottom perspective view of the mat of Figure 9 as prepared for
use;
Figure 12 is an exploded view of a mat according to the invention showing the
use of
double width boards for the core construction including the central, upper and
lower layers,
with the encapsulation artificially separated into upper and lower portions to
illustrate its
position about the core construction;
Figure 13 is a top perspective view of the mat of Figure 12 as prepared for
use;
Figure 14 is a bottom perspective view of the mat of Figure 12 as prepared for
use;
Figure 15 is a schematic illustration of an engineered wood configuration for
use as the
core construction,
Figure 16 is an exploded view of a mat that utilizes a flat core construction,
with the
encapsulation artificially separated into upper and lower portions to
illustrate its position
about the core construction;
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Figure 17 illustrates another embodiment of an industrial mat according to the
invention;
Figure 18 illustrates a core structure for the mat of Figure 17;
Figure 19 illustrates the use of elongated members to fill in the open space
of the core
structure of Figure 18;
Figure 20 illustrates another embodiment of an industrial mat according to the
invention;
Figure 21 is a bottom view of the mat of Figure 20;
Figure 22 is a view of the mat of Figure 20 with a cut-out portion to show the
construction of the core structure and its location within the encapsulating
structure; and
Figure 23 is an enlarged view of the core of structure to show the details of
the bumper
support that is attached to the core structure.
DETAILED DESCRIPTION OF THE INVENTION
The present invention now provides an improved mat that possesses better
environmental resistance due to the provision of an encapsulation that
surrounds the wood
components of the mat or the entire core construction of the mat The
encapsulation is made
of an environmentally resistant material. The term "environmentally resistant
material" means
a material that is not subject to deterioration by water, moisture or other
environmental
conditions when compared to a conventional wood material such as white oak
that is
commonly used for such mats. This term includes thermoplastic and
thermosetting materials
as disclosed herein along with various elastomeric or rubber materials.
Certain terms that are used herein are defined hereinbelow to assist in the
understanding of the invention.
The term "industrial mat" is intended to cover relatively large mats having
widths of at
least about 4 feet with lengths running from about 4 feet to 40 feet and
incorporating
elongated members, beams or other components having square or rectangular
cross sections of
sizes of at least about 1x6 to 8x8 inches with lengths from about 4 feet to as
much as 40 feet
or more. As noted, previous and current mats of this type that are
commercially available are
primarily constructed of monolithic wood.
The term "substantially" is used for its ordinary meaning to indicate that the
dimensions are not precise or exact. A skilled artisan can readily determine
what tolerances
are acceptable to provide a surface that is considered to be flat based upon
the size of the side
beams and the type of service that the mat is expected to provide. There is no
requirement
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that the beams and elongated members be flush with each other along the top
and bottom
surfaces of the mat. Typically, the term "substantially' will mean that the
top surfaces of the
beams and elongated members can vary by as much as a few inches although in
the more
preferred embodiments the variance is less than 1 inch.
Additionally, all dimensions recited herein are approximate and can vary by as
much
as 10 % to in some case 20 or 25 %. In some situations, the term "about"
is used to
indicate this tolerance. And when the term "about" is used before reciting a
range, it is
understood that the term is applicable to each recited value in the range.
Often, the
craftsmanship and engineering procedures that are followed in construction of
these mats
minimize these tolerances as much as possible or industrially practical.
In one embodiment, the present invention provides an improved mat that
possesses
structural integrity based on the properties and configuration of the core
construction as well
as abuse and abrasion resistance provided by the encapsulation. The
encapsulation, also
referred to as an encasement, typically includes two pieces, an upper portion
and a lower
portion, each generally representing half of the encapsulation. The
encapsulation will be
formed to allow the core construction to be completely accommodated therein,
with half of the
core being fit within the upper portion and half fit in the lower portion. The
tolerance
variation for the core construction is 1/8" and preferably 1/16" for all
dimensions so that it
will easily be received within the encapsulation. Once the core is placed
inside the
encapsulation, the top and bottom portions will be sealed or joined together
to completely
enclose the core therein.
In one embodiment, the encapsulation material is preferably a high density
polyethylene made by a manufacturing process known as sheetless thermoforming
technology
(STF). The resulting mat is preferably an engineered wood product mat
encapsulated in a
sealed thermoplastic encasement. The primary advantage of this product is
preservation of the
wood structure contained inside as it is sealed off from the elements prior to
experiencing
environmental conditions during use at a jobsite.
The encapsulation is preferably made of an environmentally resistant material
to
protect the core construction from degradation due to weather conditions,
typically moisture
or water from rain or snow, as well as contact with oil, gas or other
chemicals. If the mats are
to be used in a particular chemical environment, the encapsulation materials
can be selected
for resistance against that environment. Generally, however, the encapsulation
material is one
that can provide water and moisture resistance for the materials that are used
for the core
construction. Also, the encapsulation material shall be chemically resistant
to typical liquids
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found in the construction site. Thus, the mat will not absorb liquid
contaminates so that after
cleaning or washing, the mat can be removed from the work site without
transporting liquid
contaminates.
A wide range of polymeric materials can be used for the encapsulation of the
invention. These materials include:
Acrylonitrile butadiene styrene (ABS)
Acrylic (PMA)
Celluloid
Cellulose acetate
Cyclo olefin Copolymer (COC)
Ethylene-Vinyl Acetate (EVA)
Ethylene vinyl alcohol (EVOH)
Fluoroplastics (PTFE, alongside with FEP, PFA, CTFE, ECTFE, ETFE)
Ionomers
Kydex, a trademarked acrylic/PVC alloy
Liquid Crystal Polymer (LCP)
Polyacetal (POM or Acetal)
Polyacrylates (Acrylic)
Polyacrylonitrile (PAN or Acrylonitrile)
Polyamide (PA or Nylon)
Polyamide-imide (PAI)
Polyaryletherketone (PAEK or Ketone)
Polybutadiene (PBD)
Polybutylene (PB)
Polybutylene terephthalate (PBT)
Polycaprolactone (PCI)
Polychlorotrifluoroethylene (PCTFE)
Polyethylene terephthalate (PET)
Polycyclohexylene dimethylene terephthalate (PC (PC)T)
Polycarbonate
Polyhydroxyalkanoates (PHAs)
Polyketone (PK)
Polyethylene (PE)
Polyetheretherketone (PEEK)
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Polyetherketoneketone (PEKK)
Polyetherimide (PEI)
Polyethersulfone (PES)- see Polysulfone
Polyethylenechlorinates (PEC)
Polyimide (PI)
Polylactic acid (PLA)
Polymethylpentene (PIVIP)
Polyphenylene oxide (PPO)
Polyphenylene sulfide (PPS)
Polyphthalamide (PPA)
Polypropylene (PP)
Polystyrene (PS)
Polysulfone (PSU)
Polytrimethylene terephthalate (PTT)
Polyurethane (PU)
Polysulfone (PSU)
Polytrimethylene terephthalate (PTT)
Polyvinyl chloride (PVC)
Polyvinylidene chloride (PVDC)
Styrene-acrylonitrile (SAN)
The preferred materials are those that are moldable to form the upper and
lower
portions of the encapsulation, as well as those that are weldable or otherwise
capable of being
adhered, sealed or otherwise merged together so that the core construction can
be fully
encapsulated and sealed from environmental conditions.
In one embodiment, the encapsulation is molded into upper and lower portions,
which
are preferably identical. These portions are configured to be placed upon the
upper and lower
layers of the core construction. To facilitate placement of the upper and
lower portions on the
core construction, the components used for constructing the core are made of
engineered
lumber or processed white oak in order to provide close tolerances of around
1/8th of an inch
th
or less and typically around 1/16 of an inch. This assures that the upper and
lower portions
of the encapsulation will fit properly and snugly on the core construction
with the peripheries
of the upper and lower portions in contact so that they can be joined together
by welding,
adhesives, additional molding or other techniques that join and seal the
portions together.
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This assures the complete encapsulation of the construction core in order to
prevent egress of
water, moisture, chemicals or other solutions that will over time cause
degradation of the
wood materials.
Alternatively, the encapsulation can be provided in other ways, including but
not
limited to immersion coating of the entire core construction into the
encapsulation material, or
by painting or otherwise depositing encapsulation material on all surfaces and
sides of the
core construction to completely encapsulate it. The encapsulation material is
typically a
thermoplastic polymer, a thermosetting resin or an elastomeric material. For
example, the
entire core construction can be coated with a thermoplastic or thermosetting
resin to form a
solid unitary mat structure.
One method of preparation includes placing the core construction in an
enclosure and
applying a liquid plastic or elastomeric material to the core construction in
the enclosure in an
amount sufficient to form the encapsulation as the outermost surfaces of the
mat and at a
thickness sufficient to protect the core construction from environmental
conditions.
The enclosure is a large box or mold that can receive the core construction
therein and
to provide a housing for applying the plastic material therein. In one
embodiment, the core
construction is suspended in the enclosure and the liquid plastic is applied
by spraying,
painting, troweling or even pouring the plastic material onto and about the
core construction.
The core construction can be suspended by being placed on supporting
structures such
as cones, inverted cones, pins, or rods that hold the core construction in a
desired position.
The cones, pins or rods are arranged throughout the bottom of the core
construction and are
attached thereto to evenly support it in the mold in order to provide the
desired uniform
spacing above, below and around it. These supports typically have a height of
between about
0.25 and about 1" as they determine the thickness of the lower surface of the
final mat. They
are typically made of the same material as the encapsulation material so that
it bond to the
liquid encapsulation material and remain in the encapsulation in the final
mat.
In a preferred embodiment, the supporting structures are inverted cones that
has their
apexes contacting the base of the mold. These cones can be made of the same
material as the
plastic that is to encapsulate the core or of a higher melting point material
so that they do not
change shape or melt when contacted by the liquid plastic that is added. The
base of each
cone is attached to the core by an adhesive or a fastener (screw, nail or
rivet) with sufficient
cones provided so that the core is securely and uniformly supported in the
mold. When the
plastic material is introduced into the mold, it can flow around the cones and
provide a bottom
surface of the mat that only has very small dots where the cone apexes contact
the bottom of
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the mold. This provides a much better appearance than when the cone base (or a
rod or
cylinder) contacts the mold. And as the cones are made of the same material as
the
encapsulation, they blend together well in the final mat.
Alternatively, the core construction can be suspended from a wire or cord that
holds
the core construction in the appropriate position in the enclosure. The wire
or cord is
preferably made of a material that is environmentally resistant, e.g., an
engineering plastic
such as nylon or a rust resistant metal such as aluminum or stainless steel
which again can
remain in the encapsulation after the mat is made because such materials do
not detract from
the environmental resistance of the mat.
In another embodiment, the enclosure is a mold that is configured and
dimensioned to
provide a generally uniform spacing around the core construction that is
suspended therein,
and the liquid plastic material can be added into the mold and around the core
construction to
form the encapsulation around the core construction. The liquid encapsulation
material (i.e.,
plastic or elastomer) is provided in an amount that forms a thickness of the
outermost surfaces
of the encapsulation that is at least about 0.25 to about 0.5 inch although it
can be as thick as
about 1 inch. As an example, the mold can be 8'1.5" by 12'1.5" so that it can
receive a two
layer wood frame that is 8' by 12'. The wood frame can be suspended about
0.75" above the
bottom of the mold so that the outer surfaces of the resulting encapsulation
will have a
thickness on the order of about 0.75".
The upper portion of the mold is typically open and includes markings as a
fill line to
indicate the upper level of the added liquid encapsulation material. Also, the
base of the mold
is typically movable in particular upwards for assisting in ejecting the final
mat from the mold
after formation. The sides of the mold can be configured with very smooth
surfaces or with a
mold release agent to assist in allowing the mat to be ejected from the mold.
A simple
solution is to line all surfaces of the mold with a film of a plastic such as
mylar that does not
adhere strongly to the mold and that can form the outermost surfaces of the
mat. When a
molten encapsulation material is used, such as a molten plastic, the film can
be selected to be
able to resist the temperature of the molten plastic so that the final mat can
easily be
disengaged from the mold.
It is also possible to provide greater spacing so that the encapsulation
material has a
thickness of 2" to 6" at least on the elongated sides of the core
construction. This thickness
provides "bumpers" along the edges of the mat to prevent against damage of the
core
construction during use. For example, core construction of wood boards that is
7' by 11' by
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4.5" thick can be placed in a mold that is 8' by 12' and 8" deep to form 6"
bumpers around the
mat and upper and lower encapsulation thicknesses that are each 1.75" in
thickness.
One way to form the encapsulation is to fill the mold with the liquid
encapsulation
material so that the core construction is immersed into the liquid. This
assures that all
surfaces of the mat as well as at least some or most of the interstices of the
core construction
are provided with the plastic material that forms the encapsulation. The mold
can be made of
metal which is heated to soften and convert the encapsulation material to a
more flowable
liquid form. Alternatively, a solid or semisolid encapsulation material can be
placed into the
mold and heated to become softened so that the core construction can be placed
onto the
softened material to be embedded therein. Additional encapsulation material
can be placed on
the top of the core or frame construction to complete the encapsulation. These
materials can
be in sheet form that are heated before being placed in the mold. One sheet
can be placed
below the core construction and one above it. The softened sheets conform to
the core
construction and the edges stick together to complete the encapsulation.
For certain materials, such as thermosetting plastics, the heating of the mold
will
accelerate the cure of the material to more quickly form the final mat, Of
course, the
temperature would not be increased too high to reduce the setting time to one
that would not
allow a complete immersion of the mat of that would prevent the material from
entering into
the interstices of the mat.
Alternatively, if desired for certain materials, the mold can be cooled to
assist in
solidifying the encapsulation material that is injected into the mold. This
would reduce the
time for forming a mat when a molten plastic is used.
For either embodiment, the mold can be made in different movable sections so
that
after the encapsulation material forms a solid encapsulation, the mold
sections can be moved
apart or separated to recover the encapsulated mat from the mold.
Any one of a wide variety of plastic materials can be used in this method,
including
any one of the thermoplastic materials mentioned herein.
In another embodiment, the plastic material may be a liquid thermosetting
plastic
material that includes an activator or curing agent so that the liquid can be
applied to the frame
construction prior to hardening and setting to form the encapsulation. These
thermosetting
polymers form irreversible chemical bonds during the curing process.
Thermosets do not
melt, but decompose and do not reform upon cooling, so that once the
encapsulation is formed
around the core construction, it provides a very strong and durable
encasement. Preferred
thermoset materials include Epoxy, Melamine formaldehyde (MF), Phenol-
formaldehyde
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(PF), Polyester, Polyurethane (PU), Polyimide (PI), Silicone (SI) or Urea
formaldehyde (UF).
These materials can be reinforced with fibers or filler (carbon, glass, metal,
etc.) if desired.
Thus, the core construction can be coated with a thermosetting resin to form a
solid unitary
encapsulated mat structure. Instead of coating, the resin can instead be
applied by painting or
spraying. Also, the liquid resin can be placed in the mold either before or
after introduction of
the core construction therein. The supports for the mat can be thermosetting
or thermoplastic
materials that end up becoming part of the encapsulation of the mat. And as
noted herein,
providing a metal mold would allow the mold to be heated to assist in curing
of the
thermosetting material.
Elastomeric materials that are useful for the encapsulation include:
Unsaturated rubbers that can be cured by sulfur vulcanization ¨ these are
preferred
from a strength and hardness standpoint:
Natural polyisoprene: cis-1,4-polyisoprene natural rubber and trans-1,4-
polyisoprene
gutta-percha;
Synthetic polyisoprene;
Polybutadiene;
Chloropene rubber, i.e., polychloroprene;
Butyl rubber (i.e., copolymer of isobutylene and isoprene) including
halogenated butyl
rubbers (chloro butyl rubber; bromo butyl rubber);
Styrene-butadiene Rubber (copolymer of styrene and butadiene); and
Nitrile rubber (copolymer of butadiene and acrylonitrile).
Saturated (non-vulcanizable) rubbers include:
Ethylene propylene rubber (EPM);
Ethylene propylene diene rubber (EPDM);
Epichlorohydrin rubber;
Polyacrylic rubber;
Silicone rubber;
Fluorosilicone Rubber;
Fluoroelastomers;
Perfluoroelastomers;
Polyether block amides; and
Chlorosulfonated polyethylene.
The elastomeric and thermoplastic materials disclosed herein can also be
provided
with conventional filler materials to increase weight and hardness. They also
can be
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reinforced with fiberglass, other fibers, fabric or metal sheets, screening or
scrim to reduce
elongation and provide greater rigidity.
The heating of the mold can assist in the curing of those elastomeric
materials that
require vulcanization or other additives that facilitate curing.
A preferred type of elastomeric or rubber material is crumb rubber which is
prepared
by grinding worn or discarded rubber vehicle tires. This material can be mixed
with a
thermoplastic or thermosetting material and set or cured in place to form the
encapsulation
around the mat or individual wood boards.
A preferred embodiment of the encapsulation is one that is commercially
available and
is typically prepared by grinding worn or discarded rubber vehicle tires to
provide rubber
particles. During the recycling process steel and tire cord (fluff) is
removed, leaving tire
rubber particles that have a granular consistency. Continued processing
reduces the size of the
particles further. The particles are sized and classified based on various
criteria including
color (black only or black and white). The granulate is sized by passing
through a screen,
with the size based on a dimension or mesh. The particular size for the crumb
rubber of the
invention is that which is between about 0.1 and about 0.4 inches and the
particles are
generally uniform and are within that range. These sizes maximize the area of
interaction
with the polyurethane to provide optimum properties to the encapsulation.
These particles can be mixed with a thermoplastic or thermosetting
polyurethane
forming mixture and set or cured in place to form the encapsulation around the
mat. The
crumb rubber encapsulation disclosed herein can also be provided with
conventional filler
materials to increase weight, strength or hardness. These can be added to the
crumb rubber
particles prior to contacting the polyurethane forming component. In some
embodiments, the
reinforcing materials can be added to the polyurethane forming component after
contact with
the crumb rubber. This can be achieved by arranging the crumb rubber particles
and
reinforcing material in the mold prior to introducing the polyurethane forming
material
therein. The reinforcing materials include inorganic particulates such as
silica, alumina, mica
or even sand or fine gravel, fiberglass or other fibers, or fabric or metal
sheets, screening or
scrim. These materials reduce elongation and provide greater rigidity to the
polyurethane
matrix that surrounds the crumb rubber.
The crumb rubber particles are preferably held in the encapsulation by being
embedded in a polyurethane matric or binder. Polyurethane is a polymer
composed of a chain
of organic units joined by carbamate (urethane) links. While most
polyurethanes are
thermosetting polymers that do not melt when heated, thermoplastic
polyurethanes are also
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available and either one can be used in the encapsulations disclosed herein.
The thermosetting
polymers are preferred for use because they are generally harder and less
subject to
degradation or deterioration from high temperatures. These polymers are
traditionally and
most commonly formed by reacting a di- or polyisocyanate with a polyol. Both
the
isocyanates and polyols used to make polyurethanes contain on average two or
more
functional groups per molecule. Any polyol and isocyanate can be used herein
although it is
preferred that the resulting polyurethane polymer or resin be one that has
good impact and
abrasion resistance and a medium hardness so that it can withstand vehicle
movement
thereover or equipment place thereupon without permanently deforming. Routine
tests can be
conducted to determine the optimum polyurethane resin (i.e., the isocyanate
and polyol
components) for any particular industrial mat application.
The encapsulation protects the core construction from degradation due to
weather
conditions, typically moisture or water from rain or snow, as well as contact
with oil, gas or
other chemicals. Also, the encapsulation will not absorb liquid contaminates
so that after
cleaning or washing, the mat can be removed from the work site without
transporting liquid
contaminates.
The encapsulation can be provided by a number of different techniques. For
encapsulating a wood mat, a mold is prepared with a bottom surface that is
configured to
mimic the bottom surface of the two or three ply wood mat. The bottom surface
of the mold
is connected to side portions to form a well. In the particular configuration
desired for a
conventional three ply wood mat, the bottom surface of the mat has three
elongated openings
which can receive three external boards that are configured in an offset
manner in order to
allow interconnection of one mat with an adjacent mat.
The sides of the mold are smooth and essentially vertical. A slight draft
angle may be
provided to assist in removing the mat from the mold after the polyurethane
sets and cures. In
particular, the draft angles are a few degrees (i.e., 2 to 7) off vertical and
extend outward such
that the sidewalls are preferably placed at an angle of 92 or 93 with respect
to the base or
lower portion of the mold.
The top surface of the mold is a separate plate that is configured in a like
manner as
the bottom surface of the mold to provide the appropriate surface contour on
the top of the mat
as the lower mold surface provides on the bottom of the mat. The top and
bottom mold
surfaces are also configured to provide additional surface features, such as
drainage channels,
recesses for lifting elements, or openings for other peripherals. As shown in
the drawings, a
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number of water removal channels are provided and these are imparted into the
top surface of
the encapsulation because they are configured as raised areas in the mold
plate.
The mold well is first filled with approximately 0.5 to 2.5 inches of crumb
rubber
particles. The mold may include a fill line or other markings to indicate the
upper level of the
rubber crumb particulate matter that is to be introduced into the well. The
crumb rubber can
be added to the mold in many ways, such as with use of an air blower and pipe
connected to a
supply of the crumb rubber particles. Of course, the particulate matter can
simply be dumped
in the mold from pails or other sources to fill the mold well to the
appropriate level.
Thereafter, the mat is placed into the mold with the bottom surface facing the
crumb
rubber. The bottom surface of the mat is also provided with positioning pins
so that it is
supported approximately 0.25 to 2 inches above the lower mold surface. These
positioning
pins can take many different forms. In one arrangement, these pins can be
cones or other
protrusions extending from the bottom surface of the mat. In a preferred
arrangement, these
pins are bolts that are screwed into holes in the mat that extend the desired
distance away from
the bottom of the mat so that it can be placed and situated properly in the
mold These bolts
are connected to threaded openings that will later receive bolts to secure the
three offset
boards that are used to interconnect one mat to an adjacent mat. A sufficient
number of
positioning pins will be provided to properly set the mat into the mold. For a
mat that is 14
feet long, at least five to seven positioning pins will be used on each
location where a board
will be attached for interconnection of the mat. This results in at least 15
to 21 positioning
pins being provided for properly placing the mat at the correct position in
the mold. The
weight of the mat generally enables the pins to contact the bottom mold
surface but if not the
later closing of the mold will urge the mat downwardly until the pins contact
the bottom mold
surface.
When the mat does not have interlocking boards or other interlocking
structures, the
core construction can include inverted cones that has their apexes contacting
the base of the
structure for positioning the mat in the mold. These cones can be made of the
same material
as the polyurethane matrix or resin that is to encapsulate the core
construction. The base of
each cone is attached to the core construction by an adhesive or a fastener
(screw, nail or
rivet) with sufficient cones provided so that the core construction is
securely and uniformly
supported in the mold. When the polyurethane forming mixture is introduced
into the mold, it
can flow around the cones and provide a bottom surface of the mat that only
has very small
dots where the cone apexes contact the bottom of the mold. This provides a
much better
appearance than when the cone base (or a rod, bolt or cylinder) contacts the
mold. And as the
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cones are made of the same material as the encapsulation matrix, they blend
together well in
the final encapsulated mat.
After the mat is positioned in the mold, it is then covered with an additional
0.5 to 2.5
inch layer of rubber crumbs which will be used to form the top surface of the
encapsulation of
the mat. The crumb material also is provided between the sides of the mold and
the mat to
provide the side encapsulation. For this the mold is configured to be 1 to 4
inches wider than
the width of the mat. Alternatively, pins or spacers can be used to center the
mat in the mold.
Thereafter, the upper mold surface is placed upon the rubber crumb layer and
is clamped in
position so that the final encapsulation thickness is controlled to the
desired value. The top
surface of the mat can also be provided with pins in the same manner as the
bottom surface so
that the mat is precisely positioned between the top and bottom mold surfaces.
This assures
that the encapsulated mat will have an encapsulation of between at least 0.25
and 2 inches on
both the top and bottom surfaces as well as the sides of the mat. The amount
of polyurethane
components are provided so that the encapsulation typically comprises about 55
to about 80%
by weight of crumb rubber and about 20 to about 45% by weight of polyurethane.
As a specific example, the mold can be 8 feet 1.5 inches by 12 feet 1.5 inches
so that it
can receive a two layer wood frame that is 8 feet by 12 feet. The wood frame
can be placed
about 1 inch above the bottom of the mold and about 1 inch below the top mold
plate so that
the outer surfaces of the resulting encapsulation will have a thickness on the
order of 1 inch.
Conventional internal or external mold release agents can be applied to all
mold
surfaces prior to starting the process in order to assure a fast release of
the encapsulated mat
out of the mold after the mixture has fully set and cured. These agents are
generally
fluorocarbon based. Alternatively, all surfaces of the mold can be provided
with a paper layer
or plastic film so that the polyurethane does not adhere to the mold.
After the mold is secured in position, the polyurethane forming components,
i.e., a
polyol/isocyanate mixture, is introduced into the mold. The resin can be
introduced into
different sections of the mold at a number of locations. As the mixture has a
relatively low
viscosity, it will fill in all voids between the crumb rubber particles and
the mat or mold
surfaces as well as being able to flow throughout the rubber crumb layers to
saturate each
particle and the spaces around it. After the mixture sets and cures, the
rubber crumb particles
are embedded in the final polyurethane matrix that is formed. If desired, the
mold can include
vacuum lines that will assist in the assuring that the polyurethane-isocyanate
mixture flows
throughout the rubber crumb layers. Additionally, it is possible to add some
of the resin
initially when the rubber crumb is added with the two being either mixed
together or with the
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rubber crumb initially introduced into the mold followed by application of the
liquid
polyol/isocyanate mixture. As the mixture tends to set over time, the
introduction of the resin
components to the mold must be done in a relatively quick manner. For this
reason it is
preferred to introduce the material through various ports in the mold into the
crumb rubber as
soon as possible after the polyurethane and isocyanate components have been
mixed together.
The preferred polyurethane forming components are those that provide low
matrix or
resin viscosities which in turn allow for the fast injection or introduction
of the resin into the
mold while providing good wetting of and penetration between the crumb rubber
particles.
The preferred resin system can be tailored to provide a reaction or working
time of between
about 5 and about 20 minutes as this enables the resin to completely fill in
all spaces between
the crumb particles and any openings in the core construction.
Once it is confirmed that the resin has been introduced throughout the rubber
crumb
particles, the mixture is allowed to cure for a sufficient period of time to
form the
encapsulation. The curing time will depend upon the reaction or working time
and the
temperature of the mold The mold can be heated to accelerate curing if
desired, but this is
generally not necessary. The reaction between the polyol and isocyanate is an
exothermic one
and it also provides heat as well as resulting in an expansion of the material
as cures. The
fixing or clamping of the mold surfaces to prevent any outward expansion thus
concentrates
the expanding polyurethane material as a matrix in, around and between the
rubber crumb
particles in order to form a dense but compact encapsulation around all outer
surfaces of the
mat.
After the polyurethane has cured, the mold is opened by removing the top plate
so that
the mat can be removed from the mold. For this purpose, the lower mold surface
can be
provided with lifting pins or other known structures that will raise the
formed mat above the
bottom surface of the mold. This action combined with the draft angle provided
on the sides
of the mold frees the mat from being embedded in the mold and allows its
removal. In some
embodiments, the upper surface of the mat can be provided with lifting
elements which are
prevented from contacting the rubber crumb and polyurethane matrix forming
mixture so that
after curing of the resin and opening of the mold, these lifting elements are
exposed to allow a
hook from a crane or other lifting device to lift and extract the formed mat
from the mold.
The molding process can be batch or continuous as desired. For a batch
process, all
operations are conducted on a single mold. After the mold release agents are
added to the
mold, a bed of rubber crumbs is initially laid in the mold well, the core
construction is
deposited on top of the bed of crumbs, and the additional rubber crumbs are
added onto and
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around the core construction. The top mold surface is added and the entire
unit would enter
the press area where final forming would be done. After the press and curing
operations are
completed, the finished encapsulated mat can be removed from the mold.
An automated process is also possible. Several single molds are arranged on a
circular
track. A mold on a cart is provided with mold release at a first station; it
then moves to a
second station where an initial rubber crumb layer is added. The cart then
moves to a third
station where the mat is added. The cart next moves to a fourth station where
additional
rubber crumbs are added. The cart then is moved to a fifth station where the
top mold surface
is applied and the resin is introduced. The cart and fully loaded mold then
moves to a sixth
station where the press conducts the final forming and curing. Once out of the
press, the
encapsulated mat would be removed at a seventh station and the empty cart then
moved back
to the first station to start the process over again. Using seven carts allows
the activities at
each station to be conducted simultaneously and in a continuous manner on
seven different
molds
As conventional mats are generally designed with spaced boards on the upper
surface
or layer with the spacing providing water channels to drain water from the
mat, the
encapsulation may also be configured with a similar design to achieve that
purpose.
Accordingly, the upper surface of the encapsulation is not flat but is instead
configured to
provide channels that match those of a conventional board mat. Alternatively,
when the core
construction provides a flat upper surface, the upper portion of the
encapsulation can be
provided with sufficient thickness to allow water channels to be provided
therein. In fact, the
upper portion of the encapsulation can be configured to provide molded
material with spaces
in the upper or lower layer as desired.
When a mat structure is to be encapsulated that has elongated members or
boards on
the upper and lower surfaces, the lower surface of the upper mold plate and
the upper surface
of the lower mold plate may each be configured to correspond or match the
configuration of
the boards of the mat. Alternatively, when the core construction provides a
flat upper surface,
the upper portion of the encapsulation can subsequently be provided with the
water channels
or other non-flat water drainage surfaces. In fact, the upper portion of the
encapsulation can
be configured to provide molded material in place of the upper layer of
elongated members of
the core construction. In effect the mold can be configured so that the
encapsulation forms
elongated rod or board like structures that mimic the upper and or lower board
layers of a
conventional three ply wood mat. The lower portion of the encapsulation can
also be
provided with openings to receive offset boards for interlocking with adjacent
mats.
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When the core construction is flat or has openings, greater amounts of
encapsulation
material can be utilized so as to form raised crumb rubber structures on the
flat surfaces of the
core construction, or to fill in the holes or openings in the core
construction. Additionally, for
flat upper and lower encapsulation can also be provided with frit, sand or
other particulate
matter that can form a slip resistant surface. This can also be provided on
encapsulation
surfaces that include water channels if desired.
The core construction housed within the encapsulation preferably comprises two
or
three layers: a central layer for strength and rigidity; and a layer of
elongated members
positioned above or below the central layer. Preferably, three layers are
present. Suitable
materials for the components of the upper, center and/or lower layers of the
core construction
include any of the materials mentioned in this application. Wood and
preferably engineered
wood is the most preferred due to the balance of a cost and desirable
properties, but in
addition, metal, thermoplastic and thermosetting materials, and elastomeric
materials may be
used. The elastomers are usually thermosets (requiring vulcanization) but may
also be
thermoplastic. These materials may be formed as elongated members or as sheet,
grid or
grating structures. While the encapsulation does protect the core construction
from
environmental conditions, the use of materials that are other than wood
provides further
benefits in case the encapsulation is breached or damaged.
It is also possible to use a metal plate or open metal structure as the center
layer, either
alone or with upper and/or lower sheeting or even as a reinforcement of a
thermoplastic,
thermosetting or elastomeric pad. Thus, the central layer can include multiple
components
that are assembled together to form the structure to which the upper and lower
elongated
members or boards are attached.
In a preferred embodiment, the invention relates to an industrial mat
comprising a core
construction that provides strength and rigidity to the mat, the core
construction including
plural layers or plies of components at least some or all of which are wood or
engineered
wood. The woods that can be used in this mat include white oak or other
hardwoods that are
commonly included. The invention is also operable with pine or other softwoods
as these are
all protected by the encapsulation.
In addition to the wood core, the core of the mat can be made of
environmentally
resistant materials to provide even further performance advantages. This would
include one
or more elongated components or members of a thermoplastic, thermosetting
plastic or
elastomeric materials. These materials can be provided as a solid sheet or can
optionally
include apertures or open or closed cells therein or therethrough. An
appropriately sized
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grating can be used if desired. These materials optionally reinforced to
provide additional
strength or stiffness. Alternatively, one or more elongated components or
members of metal
can be used.
For certain open cell or ladder frame core construction materials,
reinforcement with
wood, metal or plastic, the cells can be filled with other materials to
provide the desired
weight to the mat. Also, reinforcements of fabrics, sheets or other cell
closing materials can
be used to improve stiffness and strength of the layer and if necessary to
retain the filler in the
cells or openings in the construction core material.
When multiple components or members are provided, they would preferably be
fastened or joined together using any acceptable technique, including the use
of nails, rivets or
bolts or even adhesives for wood or engineered wood members or components, the
bonding of
different plastic components or members together using plastic welding or the
same or a
different resin that is compatible for bonding those materials together, or by
the welding or
brazing of steel, aluminum or other metal components or members.
Preferred materials for the central layer of the core construction include:
various thermosetting materials, including Epoxy, Melamine formaldehyde (MF),
Phenol-formaldehyde (PF), Polyester, Polyurethane (PU), Polyurea, Polyimide
(PI), Silicone
(SI) or Urea formaldehyde (UF). These materials can be reinforced with fibers
or filler
(carbon, glass, metal, etc.). These can be provided as a sheet, grid, grating,
or array of beams,
or pultruded tube that optionally can be filled with foam or other filler
materials;
a thermoplastic material (any of the various plastics mentioned hereinabove)
and in
particular, HDPE, PET and SBR as disclosed in US patent 6,380,309;
a honeycomb structure with filled cells and upper and lower plate surfaces
that are
molded or otherwise constructed, as disclosed in US patent 8,061,929;
open face filled cellular structures of thermoplastics, polyolefins or
vulcanized rubber
as disclosed in US patent 6,511,257;
molded sheets of thermoplastic resin as disclosed in US patent 5,888,612; or
a reinforced plastic composite material as disclosed in US patent 4,629,358.
The edges of the core construction can be protected as disclosed in US patent
2014/0193196 or with wood or synthetic laminate to avoid mechanical damage to
core edges.
In the present invention, plastic or elastomeric materials can also be used.
These can be
molded onto the longitudinal sides of the mat or secured thereto as a separate
component that
is bolted or screwed onto the sides of the mat.
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In a most preferred embodiment, the mat includes a core construction
comprising a
central layer made of a sheet, a plurality of elongated members, a plurality
of compartments,
or combinations thereof and the entire core construction is provided with the
encapsulation.
The core construction can also include one or both of an upper layer
positioned above the
central layer and a lower layer positioned below the central layer, wherein
the upper and lower
layers are each made of a sheet, a plurality of elongated members, a plurality
of
compartments, or combinations thereof
Preferably, each layer includes a plurality of elongated members of wood or
engineered wood with the elongated members having a thickness of not less than
0.75 inches
nor more than about 12 inches and preferably between about 1 and 8 inches. For
convenience
in manufacture, all elongated members in the core construction would have
approximately the
same thickness.
Preferred materials for fiberglass reinforced plastic support structures that
can be used
as the core construction include various thermosetting materials, including
Epoxy, Melamine
formaldehyde (MF), Phenol-formaldehyde (PF), Polyester, Polyurethane (PU),
Polyurea,
Polyimide (PI), Silicone (SI) or Urea formaldehyde (UF). These materials can
be reinforced
with fibers or filler (carbon, glass, metal, etc.) as desired or necessary.
And while glass mat,
scrim or fabric is a common form of reinforcement, other conventional
reinforcement
materials can be used instead of glass or fiberglass. These additional
reinforcements are
included in the abbreviation "FRP." A convenient form of an FRP component is
as a grating.
For construction materials of FRP or metal that includes an open structure or
openings therein
or therethrough, the openings can optionally be filled or reinforced with
wood, metal or plastic
materials. The openings filled with these or other materials enables the
support structure to
provide the desired weight to the mat. Also, reinforcements of fabrics, sheets
or other closing
materials for such openings can be used to improve stiffness and strength of
the support
structure and if necessary to separately retain the filler in the openings.
It is also possible to use a metal plate or open metal structure as the
support structure
or center layer of the core construction, either alone or with upper and/or
lower plies or layers
of other materials. Thus, the structure can include multiple components that
are assembled
together to form the mat. The center layer can be used alone or it can include
additional layers
or plies of elongated components or members, such as upper and lower layers of
wood or
engineered wood boards.
When metal structures are used as the core construction or as a central layer
of the core
construction, the metal structures may include metal lath, metal sheet or
metal structures or
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fabrications in the form of frames, ladders, etc. Openings are typically
provided to reduce the
overall weight of the mat. Steel, aluminum or stainless steel are typical
metals for this use.
To reduce the weight of the mat when the construction core it is made of
metal, a honeycomb
or lathe structure may be used, or as noted the construction core may be
provided with a
plurality of openings. For very open structures, the openings can be filled as
noted above with
a material that is lighter than the metal to maintain the weight of the
structure at a desired
level.
Any openings or open structures of the core construction can be covered with
upper
and/or lower sheeting to retain filler therein. Any material can be used for
the sheeting as the
metal core is providing the necessary strength and rigidity to the mat.
Typically, the sheeting
may be plywood, plastic, metal or composite material, and can be solid or in
mesh form. The
sheeting can be attached to the mat by bolting or by an adhesive. The sheeting
and core can
be maintained in position by being sandwiched between the outer layers, with
the entire
support structure held together by bolting. If necessary, holes for the bolts
can be drilled
through the metal plate or sheeting to facilitate assembly by allowing passage
of the bolts
therethrough.
And in a further embodiment of the invention, the provision of apertures or
openings
in the core construction enables the encapsulation material to be received
therein, thus
forming stronger bonding of the encapsulation to the mat as it not only
encapsulates the outer
surfaces of the mat but it also penetrates and passes through the openings of
the core structure
to join the top surface of the encapsulation to the bottom surface.
Preferably, the upper, central and lower layers are nailed, bolted or riveted
together to
form the core construction. For a core construction where the interlocking
boards (boards 3, 6
and 9 of the single width construction and the three 6" boards of the double
width
construction) are not included, these may be provided on top of the
encapsulation. They can
be bolted or nailed onto the core construction through the encapsulation, but
with appropriate
sealing of the encapsulation with additional material to prevent water or
chemical penetration
into the core construction. This arrangement provides two additional benefits.
First of all, the
boards placed outside of the skin are easily replaceable if damaged while the
protected core
remains intact. Also, this arrangement facilitates the placement of lifting
elements included in
boards 3 and 9 of the single width construction or in the first and third 6"
boards of the double
width construction.
Another preferred construction includes three layers of engineered lumber.
Engineered lumber, also known as composite wood, man-made wood, or
manufactured board;
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includes a range of derivative wood products which are manufactured by binding
or fixing
strands, particles, fibers, or veneers or boards of wood, together with
adhesives, or other
methods of fixation to form the composite material known as engineered lumber.
These
products are engineered to precise design specifications and tolerances which
are much more
controlled than ordinary wood products and meet various national or
international standards
and these controlled dimensions are carried over into the construction of the
mat. Typically,
engineered wood products are made from the same hardwoods and softwoods used
to
manufacture lumber.
There are three types of engineered wood that can be used in the present
invention:
parallel strand laminate (PSL), which is a beam that can be manufactured up to
about 12x12 inches in any length due to the production of the beam by
a continuous process;
layered stand laminate (LSL), which is a billet that can be made at
thicknesses
of from about 1" to 4", in widths from about 2 inches to 54", and in
lengths of about 8 feet to 64 feet; and
layered veneer laminate (LVL) which is also a billet that can be made up to
about 4 feet square by any length.
The preferred types of engineered lumber are laminated strand lumber (LSL)
layered
veneer laminate (LVL). The thickness of these lumber beams will be what is
called 2x8
inches, which is actually approximately 1.75 inches thick but may be between
1.5 and 3
inches. Length can be as desired but will preferably be 12, 14 or 16 feet. The
width of the
LSL or LVL boards will vary depending upon location within the three layer
mat. That is,
width of the top and bottom layer boards will be approximately 8 inches
(single width) or 16
inches (double width). Approximately means they may be slightly less such as
7.5 to 8.5
inches or 15 to 17 inches. Of course, as the LSL or LVL is manufactured, any
particular
thickness, width and length can be selected, but the preferred dimensions
disclosed herein
approximate those of conventional white oak mats which are in extensive use in
the industry.
A typical thickness for the mat is approximately 6" to 8", with the central
layer providing a
thickness of about 1" about 6" and preferably about 2 to about 4" and the
upper and lower
layers providing a thickness of about 1" to about 3". Of course, the
dimensions can vary
depending upon the specific end use intended for the mat.
The center layer will be approximately 4 to 8 feet by 12, 14 or 16 feet. The
center
layer may be made of LSL, LVL or other boards that are oriented
perpendicularly to the
boards of the top and bottom layers. The number of top, bottom, and center
boards will be
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dictated by the final dimensions of the mat for the particular application or
end use. When the
center layer is a sheet or plate, the boards of the upper and lower layers can
be oriented in the
same or a different direction. Generally, for manufacturing simplicity, the
boards of these
layers are oriented to be parallel or perpendicular to each other. Other more
complex angled
board arrangements may also be used without departing from the teachings of
this invention.
The engineering wood is preferred when close tolerances are required for the
core
construction. This is primarily necessary for preformed upper and lower
encapsulation
sections so that the mat can be assembled easily. As noted, after the core
construction is
placed between the upper and lower sections, the perimeter of those sections
is sealed by
welding or adhesives.
in a most preferred embodiment, the mat includes a core construction
comprising a
central layer, an upper layer positioned above the central layer and a lower
layer positioned
below the central layer, wherein each layer includes a plurality of elongated
members of wood
or engineered wood having thickness and width dimensions of approximately
about 2" by
about 8", and with each having a modulus of 1.6 M psi + 20% up to about 2 M
psi + 20% and
with the elongated members of the upper and lower layers oriented parallel or
perpendicular to
each other. Also, the core construction is made of materials that provide a
load bearing
capacity that is able to withstand a load of at least 600 to 800 psi without
damaging or
permanently deforming the core construction.
The core construction can include one, two or three layers as desired or
necessary for a
particular installation. The most preferred construction includes three layers
as noted herein.
When elongated members are used for the upper and/or lower layers of the core
construction, they provide additional weight to the mat and can be configured
in different
ways:
a single width construction may be used where eleven 6" wide (by 12' 14' or
16' long)
boards are provided in the upper and lower layers with three boards (nos. 3,
6, and 9) in the
lower layer offset for interlocking; or
a double width construction may be used where four 12" wide (by 12 or 16'
long)
boards are provided in the upper and lower layers: each one separated by a 6"
board with the
three 6" boards in the lower layer offset to provide interlocking.
The boards can be made of wood or engineered lumber (preferably with a
tolerance of
+1/16") or they can be made of tubes of metal of a thermoplastic or
thermosetting material,
with pultruded thermosetting tube being one example of a preferred alternative
material.
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The core constructions may include those made of white oak as disclosed in US
patents 4,462,712 (three layer) and 5,822.944 (two layer).
Other wood species can be sued as
desired. Additional processing of the wood may be required to achieve the
desired tolerances
for optimum fitting of the construction core when encapsulation pieces are
used.
An alternative embodiment relates to the provision of an encapsulation or
coating of
one or more of the environmentally resistant materials disclosed herein around
a sheet, beam
or board mat component of wood or engineered wood. The encapsulation or
coating is
applied prior to the assembly or incorporation of the component into the mat.
The
encapsulation or coating is applied to all exposed surfaces of the component
so that moisture
cannot get into the wood and eventually cause deterioration or rotting. The
thicknesses would
be the same as in other embodiments, namely, about 0.25 to about 0.5 inch or
even as thick as
about 1 inch or more if desired for particular applications.
In a more general embodiment, the core construction housed within the
encapsulation
comprises two or three structural layers: a central layer for strength and
rigidity; and a layer of
elongated members positioned above or below the central layer. Preferably,
three layers are
present. Suitable materials for the components of the upper, center and/or
lower layers of the
core construction include any of the materials mentioned in this application.
Wood and
preferably engineered wood is the most preferred due to the balance of cost
and desirable
properties, but in addition, metal, thermoplastic and thermosetting materials,
and elastomeric
materials may instead be used.
Referring now to the Figures, Figure 1 illustrates mat 100 that includes an
upper skin
105 and lower skin 110 which are used to surround and encapsulate core
construction 115 and
form the encapsulation. The core construction includes a rectangular sheet 120
of wood,
plywood, or non-wood material. On the top surface of sheet 120, boards 125 are
applied to
the sheet 120 by nailing, screwing, bolting or combinations thereof. On the
bottom surface of
sheet 120, boards 130 are also applied by nailing, screwing or bolting of
boards 130 to the
sheet 120. Preferably LSL boards are used for the upper and lower boards to
obtain a good
balance of dimensional tolerance, cost and performance.
When bolting is used, the bolts can extend from the upper boards 125 to the
lower
boards 130 through the sheet 120. The nails, screws or bolt heads and nuts are
recessed below
the top surface of boards 125 and below the bottom surface of boards 130 to
present relatively
smooth upper and lower surfaces of the core construction 115.
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Alternatively, the boards can be attached to the sheet 120 by an adhesive or
other
means that provide a secure attachment. For example, when the core
construction is made of
a thermosetting material, the sheet and boards can be made of the same
material in a unitary
component. The same is true of a welded metal core construction.
A first embodiment of the invention is shown in Figures 1-4, where the
encapsulation
comprises two thermoplastic skins forming upper and lower portions of the mat
surrounding a
core construction made of wood boards.
As shown in Figure 1, eight (8) boards are used, with each two board pair
separated by
a space that would accommodate another board. Both the upper and lower boards
that are
attached to the sheet 120 are arranged in the same way so that the same size
skin portions can
be used to encapsulate the top and bottom of the core, thus allowing a single
mold to provide
moldings that can be used as either the upper or lower skin portions.
Spaces are provided for the third, sixth, and ninth boards (135, 140, 145,
respectively)
of the upper portion of the mat to allow such boards to be applied to the skin
portions after
encapsulation of the core construction 115. Also, space is provided for the
third sixth and
ninth boards (155, 160, 165, respectively) of the lower portion of the mat to
allow interlocking
of the mat to an adjacent mat. The boards 155, 160 and 165 are applied to the
lower skin
portion in order to extend outwardly from the end of the mat to be received in
a space in the
lower skin of an adjacent mat. Although these additional boards are attached
to the mat by
screwing or bolting, any holes made through the skin are also sealed to
prevent introduction of
water or moisture into the core construction.
Lifting elements 150 are provided on the third and ninth boards of the upper
skin
portion. These lifting elements 150 are configured as D shaped rings which are
attached to the
boards in recesses 170 so that the lifting element 150 can remain flat when
the mat 100 is in
use. Two lifting elements are shown but a skilled artisan can determine how
many elements
are needed for lifting of any particularly sized mat. If desired, lifting
elements can also be
provided on the boards attached to the lower skin portion 110 for versatility
in the handling
and transportation of the mat. The lifting elements are provided on the boards
that are
attached to the skin portion so that if the lifting elements or boards are
damaged they can be
easily removed and replaced.
The provision of single width boards enables the upper and lower moldings to
have
water channels 175 on the upper surface of the skin to drain water from the
mat.
Figure 2 illustrates the final shape and configuration of the mat 100 after
assembly.
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Figure 3 illustrates a second mat 200 according to the invention. In this mat,
double
width boards 225, 230 are used in place of the single width boards 125, 130 of
Figure 1. This
results in upper 205 and lower 210 skin portions that have a wider molded
segments to
accommodate the double width boards. As in the embodiment for Figure 1, space
is provided
for the additional boards that include the lifting elements and that provide
interlocking. As a
number of the same components are used, the same numerals used in Figure 1 are
used to
designate the same components for the mat of Figure 3.
Figure 4 illustrates the final mat 200 after assembly.
The drainage channels 175 provide an advantage for mat 100 compared to mat 200
when the mats are to be used in an environment that will experience rainy or
snowy weather
conditions. For application of the mats in a dry environment, mat 200 is
preferred because it
is easier to manufacture.
An additional embodiment is illustrated in Figures 5-8, wherein a wood mat is
suspended in a tank or mold that receives polymer material that encapsulates
the mat Figure
5 is a perspective view of a mold 300 that is used for holding a mat frame
construction 320
therein prior to receiving plastic material and forming the encapsulated mat.
The mold 300
includes sides 315, a base and an open top in the form of a rectangle that has
a slightly greater
perimeter than that of the frame construction 320. The frame construction 320
is supported in
the mold by a number of inverted cones 325 that raise the frame construction
320 above the
base of the mold by a distance that corresponds to the thickness of the
plastic encapsulation.
Also, the frame construction 320 is spaced from the sides 315 of the mold by
the same
distance. As noted herein, the mold and frame construction are configured with
dimensions
that provide a clearance of 0.25 to 1" about the frame construction.
To form the encapsulated mat, a liquid plastic material is filled into the
mold 300 to
surround the mat and fill any interstices between the boards of the frame
construction 320. As
disclosed herein, the plastic may be a molten thermoplastic or a catalyzed
liquid thermosetting
resin. To achieve the desired thickness of the encapsulation on the upper side
of the mat, a fill
line 350 is provided. The added plastic material is then allowed to cool or
harden to form the
mat 360.
A hydraulic lifting member 370 and support pad 380 are provided beneath the
base of
the mold to lift the base upwards after the mat is cooled. The base is
removably associated
with the sides 315 in a way that retains the liquid plastic therein when
forming the mold and
then which allows the lifting member to raise the formed mat above the sides
for ejection and
recovery of the final mat. As noted herein, the inner sides of the mat can be
provided with a
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film that does not adhere or only slightly adheres to the surfaces of the mold
so that the mat
can be lifted easily after formation.
Figure 6 is a cross sectional view of the mat 360 after it is formed and
removed from
the mold of Figure 5. The mat 360 has a relatively uniform thickness around
the frame
construction 320 such that the frame construction 320 is protected from the
elements during
use. This enables a frame construction made of wood to provide a much longer
service time
than if the wood was exposed to water or moisture which over time can cause
the wood to rot
or degrade.
Figure 7 is a view of an encapsulated mat 400 that includes single width
boards. The
mat includes encapsulation 410 which surrounds all internal boards of the
frame construction
that provides strength to the mat. The encapsulation 410 is formed with a
number of
longitudinal recesses 420 that run the length of the mat to provide allow
drainage of moisture
from the surface of the mat during use. Larger recesses are provided for the
attachment of
boards 430. On the upper surface of the mat, boards 430 complete the upper
surface to
provide a flat, weight bearing arrangement. Some of these boards 430 may be
provided with
lifting elements 450 to allow lifting or moving of the mat. These boards 430
are attached to
the encapsulated structure by nails, screws or rivets. Alternatively, these
boards 430 may be
bolted to the mat after drilling holes therethrough to receive the bolts.
Appropriate nuts or
other fasteners can be provided as needed.
On the lower surface of the mat, boards 440 are provided. These boards are
offset to
allow interlocking of one mat to an adjacent mat. At one end of the mat 400,
the ends of
boards 440 extend beyond the end of the mat as shown. On the opposite end of
the mat, the
recesses are open by the same length as the stick out portion of the boards
440 on the opposite
side in order to receive board ends from an adjacent mat. Boards 440 are also
attached to the
mat by nails or screws, or they can be bolted to the mat in the same way or in
conjunction with
the attachment of boards 430.
Figure 8 is a view of an encapsulated mat 500 that includes double width
boards. The
mat includes encapsulation 510 which surrounds all internal boards of the
frame construction
that provides strength to the mat. The encapsulation 510 is formed with a
number of
longitudinal recesses that are provided for the attachment of boards 520. On
the upper surface
of the mat, boards 520 complete the upper surface to provide a flat, weight
bearing
arrangement. Some of these boards 520 may be provided with lifting elements
550 to allow
lifting or moving of the mat. These boards 520 are attached to the
encapsulated structure by
nails, screws or rivets. Alternatively, these boards 520 may be bolted to the
mat after drilling
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holes therethrough to receive the bolts. Appropriate nuts or other fasteners
can be provided as
well.
On the lower surface of the mat, boards 530 are provided. These boards are
offset to
allow interlocking of one mat to an adjacent mat. At one end of the mat 500,
the ends of
boards 530 extend beyond the end of the mat as shown. On the opposite end of
the mat, the
recesses are open by the same length as the stick out portion of the boards
530 on the opposite
side in order to receive board ends from an adjacent mat. Boards 530 are also
attached to the
mat by nails or screws, or they can be bolted to the mat in the same way or in
conjunction with
the attachment of boards 520.
To form the recesses on the mats 400, 500 of Figures 7 and 8, the mold base is
provided with a non-uniform raised surface that corresponds to the shape and
position of the
recesses of the mat. This provides the recesses in the lower surface of the
mat. On the upper
surface of the mat, a lid is provided which is also configured with a non-
uniform raised
surface that corresponds to the shape and position of the recesses for the top
surface of the
mat. The mold lid is placed on the liquid plastic after the mold is filled.
The lid surface is
also provided with a plastic film so that the mat encapsulation does not stick
to it after
formation of the mat.
The encapsulation protects the frame construction from degradation due to
weather
conditions, typically moisture or water from rain or snow, as well as contact
with oil, gas or
other chemicals. If the mats are to be used in a particular chemical
environment, the plastic
materials can be selected for optimum resistance against that environment.
Generally,
however, the plastic material is one that can provide water and moisture
resistance for the
wood materials that are used for the frame construction. Also, the plastic
material shall be
chemically resistant to typical liquids found in the construction site. Thus,
the mat will not
absorb water or other liquid contaminates so that after cleaning or washing,
the mat can be
removed from the work site without transporting the liquid contaminates.
While the encapsulation provides a unitary structure, in use it is envisioned
that the
encapsulation may eventually experience damage due to handling, installation
and use in
supporting heavy equipment or vehicles. In some cases it will be possible to
patch or
otherwise repair the damaged areas while still retaining a sealed structure
that will resist
moisture penetration. In some cases, however, it will be necessary to
completely remove the
damaged encapsulation such that a knife or hot wire can be used to cut through
an
encapsulation of a thermoplastic material for complete removal and replacement
when
necessary to remediate damaged encapsulation material.
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As mats are generally designed with water channels on the upper and lower
surfaces or
layers to drain water from the mat, the molds are typically configured with
the same design to
achieve that purpose. Accordingly, the upper and lower surfaces of the
encapsulation are not
flat but instead are configured to match the surface provided by the frame
construction. The
provision of the same design on the top and bottom surfaces of the mats allows
the top surface
to receive boards to complete the surface and the bottom surface to receive
the interlocking
boards, which in effect are the same boards that are used on the top except
that they are offset
by 6" or so to allow interlocking with an adjacent mat.
The boards can be attached to the mat using self-tapping lag screws or rivets.
As the
frame construction is precisely positioned in the mold, the points where the
boards intersect is
known. Thus, the interlocking boards can be attached to the mat by screwing or
riveting into
the frame construction. And as noted herein, if other frame constructions
including those
made of fiberglass reinforced plastic are used, the interlocking boards can be
attached in the
same manner. If the frame construction is made of metal, it can be provided
with bolting
extending therefrom towards the top and bottom surfaces of the mat in the
recesses to allow
attachment of boards that are provided with holes to receive the bolts. The
boards can then be
secured to the mats using appropriate nuts and washers that engage the
threaded ends of the
bolts.
For any of the frame constructions disclosed herein, the weight of the mat can
be
controlled by the provision of particulate material therein. For example, a
screen or mesh can
be placed in the frame construction so that particulate material can be added
and retained
therein prior to the addition of the plastic material into the frame
structure. This combination
provides further benefits to the mat, including greater stiffness, strength,
and control of the
weight, either higher or lower depending upon the intended application of the
mat.
Figures 9-17 illustrate another encapsulated mat, this one having an
encapsulation of
crumb rubber particles in a polyurethane matrix. Figure 9 is an exploded view
of an
encapsulated mat 600 that shows the encapsulation in two artificial sections,
namely an upper
portion 605 and lower portion 610 which are used to surround and encapsulate
core
construction 615. Of course, the encapsulation is applied to completely
surround the core
construction but is shown herein as cut and separated so that the core
construction 615 can be
seen. The core construction may instead include a rectangular sheet 620 of
wood, plywood,
engineered wood, or a non-wood material such as a thermosetting resin or a
metal. On the top
surface of sheet 620, boards 625 are applied to the sheet 620 by nailing,
screwing, bolting,
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adhesives or combinations thereof. On the bottom surface of sheet 620, boards
630 are also
applied by nailing, screwing, bolting or adhesive joining of boards 630 to the
sheet 620.
Preferably hardwood or LSL boards are used for the core construction with LSL
used
for the upper and lower boards to obtain a good balance of dimensional
tolerance, cost and
performance. Of course, hardwood can be used throughout for the lowest cost
construction.
When bolting is used, the bolts can extend from the upper boards 625 to the
lower boards 630
through the sheet 620. The nails, screws or bolt heads and nuts are recessed
below the top
surface of boards 625 and below the bottom surface of boards 630 to present
relatively smooth
upper and lower surfaces of the core construction 615.
Alternatively, the boards can be attached to the sheet 620 by an adhesive or
other
means that provide a secure attachment. This allows wood boards to be used
with a metal or
FRP central layer. When the core construction is made of a thermosetting
material, the sheet
and boards can instead be made of the same material to form a unitary support
structure. The
same is true of a welded metal core construction. These materials can be mixed
or matched
depending upon the intended use of the mat. As noted, this preferably
includes:
(a) One or more layers of engineered wood not less than about 1 inch nor more
than
about 12 inches thick;
(b) A grating material of a thermosetting plastic material of a polyester,
epoxy or the
others mentioned herein. The thermoset material may be reinforced with
fiberglass, carbon,
etc. Or it may be an unreinforced engineered polymer. Glass fiber
reinforcement in an
amount of about 50 to about 75% provides a high stiffness to the support
structure.
Preferably, the grating would be between about 2 and about 4" thick to provide
sufficient
strength for the core construction at a relatively low weight for the mat;
(c) A thermosetting plastic material in the form of pultruded rods. These can
be of
solid or hollow tubular construction and are preferably square or rectangular
in cross section.
If desired, the openings can be filled with form or particulate matter; or
(d) Any type of metal in whatever thickness is necessary, with steel being the
most
economical.
For the preferred wood mats, as shown in Figure 9, eight (8) boards are again
used,
with each two board pair separated by a space that would accommodate another
board for
interlocking of the mat with an adjacent mat. Both the upper and lower boards
that are
attached to the sheet 120 are arranged in the same way so that the same size
mold portions can
be used to form the encapsulation on the top and bottom surfaces of the core
construction.
Alternatively, the upper surface of the core construction can be provided with
boards in the
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spaces so that the interlocking boards are provided only on the lower surface
of the mat. For
this, the upper mold part would be configured differently from the lower mold
part.
As shown, spaces are provided for the third, sixth, and ninth boards (655,
660, 665,
respectively) of the lower portion of the construction core 615 to allow such
boards to be
applied to the encapsulation of the core construction 615 to thus allow
interlocking of the mat
to an adjacent mat. The boards 655, 660 and 665 are applied to the
encapsulation in order to
extend outwardly from the end of the mat to be received in a space in the
encapsulation of an
adjacent mat. Although these additional boards are attached to the mat by
screwing or bolting,
any holes made through the encapsulation are also sealed or provided with 0-
rings to prevent
introduction of water or moisture into the wood components or members of the
core
construction and degradation of the wood over time.
Openings 670 for receiving lifting elements are provided on the encapsulation
upper
surface 605. These lifting elements may be configured as D shaped rings which
are attached
to the boards in recesses 670 so that the lifting element can remain flat when
the mat 600 is in
use. Two openings for lifting elements are shown but a skilled artisan can
determine how
many elements are needed for lifting of any particularly sized mat. If
desired, openings can be
provided for lifting elements to be installed on the boards attached to the
lower surface of the
mat for versatility in the handling and transportation. The lifting elements
are provided on the
boards that are attached to the encapsulation so that if the lifting elements
or boards are
damaged they can be easily removed and replaced.
The provision of single width boards enables the upper and lower moldings to
have
water channels 675 on the upper surface of the encapsulation to drain water
from the mat.
Figures 10 and 11 illustrate the final shape and configuration of the mat 600
after
assembly. The encapsulation covers the entire mat with the exception of the
three interlocking
boards 655, 660, 665 on the bottom surface that are added after the core
construction is
encapsulated.
Figure 12 illustrates a second mat 700 according to the invention that uses
three layers
of wood for the core construction. In this mat, double width boards 725, 730
are used in place
of the single width boards 625, 630 of Figure 9. As in Figure 9, the
encapsulation is shown in
two artificial sections, namely an upper portion 705 and lower portion 710
which are used to
surround and encapsulate core construction 715. As in the embodiment for
Figure 9, space is
provided for the boards 655, 660, 665 on the lower portion 710 of the
encapsulation that
provide interlocking and openings 670 are provided for attachment of lifting
elements.
Openings 650 may also be provided on the boards of the core construction 715
beneath
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openings 670 of the encapsulation so that the lifting elements can be directly
attached to the
core construction 715. As a number of the same components are used, the same
numerals
used in Figures 9-11 are used to designate the same components for the mat of
Figures 12-14.
Figures 12-14 illustrate the final mat 700 after assembly. The drainage
channels 675
provide an advantage when the mats are to be used in an environment that will
experience
rainy or snowy weather conditions. These channels are provided by including
projections or
protruding segments on the mold. For application of the mats in a dry
environment, these can
be optional although they are preferred since the mats are often used in wet
environments.
And while offsetting of certain boards is shown for providing an interlocking
with
adjacent mats, this is not always needed such that interlocking can be
considered to be an
optional yet desirable feature. Interlocking is often preferred to avoid
staking of the mats to
the ground or to avoid including other more complex components for use in
connecting
adjacent mats together. The interlocking boards are provided on at least the
lower surface of
the mat, but in certain embodiments, they can be provided on both the lower
and upper
surfaces of the mat as shown in the figures. And interlocking boards can be
entirely omitted if
desired, with the core construction including boards in all spaces prior to
being encapsulated.
When engineered lumber is used, there are a number of configurations which are
ideally suited for use of that material as the core construction of the
present invention. In
particular, LVL is used for these embodiments. A preferred embodiment is shown
in Figure
15, wherein the structure of the core construction is a 3 inch thick, 4 foot
wide by 8 foot long
block that is made by multiple strips of unidirectional veneers that are
adhered together to
form the block. First of all, two base blocks that are 1.5 inches thick and
are 4 foot wide by 4
foot long are prepared. These blocks are joined together along their width to
form a 4 foot by
8 foot by 1.5 inch thick combined block structure. This combined block
structure is
reinforced by adding two 1.5 inch thick, 4 foot wide by 2 foot long sections
on the upper
surface of the combined block structure: one at the forward end of the mat and
one at the rear
end of the mat. Between these sections is a middle section that is 1.5 inch
thick, 4 foot wide
and 4 foot long located between the forward and rear sections.
For greatest strength in any of these embodiments, most unidirectional veneers
are
oriented in the machine direction with 5 to 30% and preferably 20 to 25% of
the veneers
oriented in the cross machine direction. That geometry sets up some very
impressive
physicals for the combined structures.
The structure shown in Figure 15 is a "single board" that would require no
fastening
mechanisms and that can be just dropped onto the bed of rubber crumbs in the
mold.
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Furthermore, the costs of the structures of these embodiments will be on the
order of oak or
other hardwoods.
Preferred overall mat dimensions for wood mats are approximately 8' wide x 6"
tall
and are either 12 ft, 14 ft or 16 ft in length. The interlocking feature will
extend the length of
the mats by about 1 ft at three locations at one end of mat. As noted, US
patent 4,462,712
discloses mats which contain interlocking fingers and recesses which are
preferred for use in
the present invention. The mats typically include three (3) layers of
individual wood or
engineered wood boards having cross section dimensions of 1.75" by 8".
The spacing between individual boards or components in the upper layer is
preferably
approximately 1.25" to allow water to drain from the mat. This spacing is
retained in the
encapsulation. The slip resistance of the mat is improved by the draining of
the excess water,
especially when use in locations that experience heavy rain or snow
conditions.
Figure 16 illustrates these additional embodiments of the invention. As in
Figures 9
and 12, the encapsulation for the mat 800 is shown in two artificial sections,
namely an upper
portion 805 and lower portion 810 which are used to surround and encapsulate
core
construction 815. For this embodiment the core construction 815 is shown as a
plate or sheet.
The material for this plate or sheet can be any one of those mentioned herein
including
engineered wood, steel or other metals, or a reinforced thermosetting resin
(e.g., reinforced
with glass or other known material to provide increased strength). The sheet
or plate has
sufficient properties to provide strength and rigidity to the mat. The sheet
or plate may
include positioning pins or cones so that it would be properly placed in the
mold after the
mold is provided with the rubber crumb particles. As in the embodiments for
Figures 9-14,
space is provided for the boards 655, 660, 665 on the lower portion 810 of the
encapsulation
that provide interlocking and openings 670 are provided for attachment of
lifting elements.
The upper and lower surfaces of the mold would be provided with protrusions
that
impart drain channels 875 into the top and bottom surfaces of the
encapsulation. Unlike the
mats of the other embodiments, the upper and lower surfaces are actually made
of elongated
strips of cured polyurethane matrix/rubber crumb rather than a coating over
the boards or
elongated members for the core construction. These strips, which are in
reality formed when
the resin is introduced into the rubber crumb particles, can be as thick as 2
to 4 inches on each
of the top and bottom services and of the same length as the elongated members
of an upper or
lower ply of a three ply wood mat. These strips of course require much more
rubber crumb
than in the other embodiments where the encapsulation is in effect a coating
over a three layer
mat.
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Instead of linear drain channels 675 as shown, the mat surfaces can be
prepared with
different configurations that provide recessed areas for drainage of water for
better traction of
vehicles or personnel that move upon the mats. These drain channels can be
linear in parallel
arrangement as shown or additional drain channels can be provided at 90 degree
or other
angles to the parallel channels. As the core construction is flat, the raised
crumb rubber
portions can be provided as segmented shapes of other than rectangles, such as
triangles or
other polygons. The shapes can take the form of raised or recessed letters,
numbers, writing
or other combinations of alphanumeric characters. Alternatively, the surface
can be provided
with grit, particles or other granular material that would provide a more slip
resistant surface.
All of these provide better traction when personnel or equipment are moving
upon the mat.
Figures 17-23 illustrate an additional encapsulating material that is used to
encompass
the entire mat including any spaces therein to form the encapsulated mat.
Figures 17 and 18
illustrate a preferred embodiment of the invention wherein an industrial mat
900 is shown that
includes therein a frame 1000 that is provided as a core structure and which
is enclosed within
an encapsulating structure 905 of a plastic material. As noted herein, the
frame 900 provides
the strength and backbone of the mat while the encapsulating structure 905
provides
environmental resistance and protection of the frame and core.
The encapsulating structure 905 can be made of a variety of materials as noted
herein.
A wide range of thermoplastic, polymeric, thermosetting or elastomeric
materials as disclosed
herein can be molded or cast to the desired size and thickness of the mat. The
encapsulating
structure is typically molded as a unitary structure around a strength or
support core. These
materials can also be provided with conventional fillers to increase weight
and hardness.
They also can be reinforced with particulates, fibers such as glass, fabric or
metal screening or
scrim to reduce elongation and provide greater rigidity.
The top 910 and bottom 920 surfaces of the mat are also provided with drainage
channels 915, 925 which are generally rectangular in shape and which typically
have a width
of 1.25 inch and a depth of 1 inch. It is of course also suitable to use U-
shaped channels.
Figure 17 also illustrates lifting elements 950 on the upper surface of the
mat. These
lifting elements 950 are configured as D shaped rings which are attached
through the
encapsulation to cross-members in recesses 970 so that the lifting element 950
can remain flat
when the mat 900 is in use. Two lifting elements are shown but a skilled
artisan can
determine how many elements are needed for lifting of any particularly sized
mat. If desired,
lifting elements can also be provided on the boards attached to the lower
surface of the
encapsulation for versatility in the handling and transportation of the mat.
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The core structure is preferably configured as a frame 1000 as shown in Figure
18.
This frame 1000 includes side members 1005 and 1010 which can be made of any
one of a
number of different materials. In one embodiment, side members are rectangular
tubes made
of metal such as steel or of an FRP pultrusion. The open areas of the tubes
can be filled with
additional material such as a polyurethane foam, sand, rubber crumb or other
particulate
material to provide additional support to the tube or weight to the mat. These
side members
1005, 1010 are configured and dimensioned to provide sufficient strength to
the sides of the
mat and to resist forces imparted thereto when moving the mat or when heavy
equipment is
driven over the sides of the mat. Alternatively, these side members may be
made of a solid
material instead of a tube, with wood or engineered wood being preferred for
this alternative.
And as noted herein, the top, bottom and outer side portions of the side
members are provided
by a predetermined thickness of at least 0.25 or 0.5 inch to as much as 5
inches of the material
of the encapsulating structure. In certain embodiments, however, the
thickness of the
encapsulating material on the side and cross members can be as little as 0.125
inch to as much
as 0.6 inch, especially when polyuria or polyurethane is used as the
encapsulating material.
Greater thicknesses, while not undesirable, are simply not necessary and add
additional cost
without additional benefits for that material.
The frame 1000 also includes a plurality of cross members which provide
structural
support for the side members. These cross members may also be made of
rectangular tubes of
metal such as steel or of an FRP pultrusion or of wood or engineered wood.
Specifically, the
forward end of the mat includes cross member 1015 while the rear portion of
the mat includes
cross member 1025 forming a generally rectangular frame. Additional cross
members 1035,
1045 may be provided within the rectangular frame depending upon the size of
the mat to
provide additional reinforcement to the side members to form a more robust
core structure that
provides overall strength to the mat. The number of cross members depends upon
the size and
thickness of the final mat.
The cross members preferably are made of a material that is the same as that
of the
side members 1005, 1010 to facilitate formation of the frame by joining
similar materials
together, but it is also possible for the cross members to be of a different
material. When
different materials are used, the cross and/or side members are configured in
a way that would
allow their connection by bolting to form the frame. For example, the cross
members can be
provided with separate L-shaped flange members at each end so that one part of
the flange is
bolted to the cross-member and the other end is bolted to the side member. Of
course, many
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other arrangements can be made by skilled artisans using good structural
engineering practices
and all are considered to be included in the scope of the present invention.
The frame can be made of steel, wood, engineered wood or fiberglass reinforced
plastic in the form of beams or tubular structures. When the frame is made of
tubular
structures, those structures may be filled with a reinforcing material that
provides strength or
reinforcement. Also, the frame can includes elongated members therein to fill
in a portion of
the space between the side and cross members of the frame. These elongated
members can be
made of wood, engineered wood, end grain wood or open or filled thermosetting
pultrusions,
or a particulate filler of recycled rubber tire material, sand, gravel, earth
or combinations
thereof.
As shown in Figure 18, the side members of the mat have a greater height than
the
cross members. Thus, the cross members are connected so that they are
positioned in the
center of the side members, with space provided both above and below the cross
member so
that the side members are taller than the cross members on both the top and
bottom of the mat.
This arrangement provides space for the channels 915, 925 in the upper 910 and
lower 920
surfaces of the mat shown in Figure 17 so that they do not contact the cross
members and
expose them to the elements during use of the mat. In fact, the encapsulating
structure 905
provides a thickness of at least 0.25 inch and preferably 1 inch around and
about all surfaces
of the frame members.
When the frame members are made of steel, they can be simply welded together
to
provide the frame structure. Of course, if the frame members are made of FRP,
they would be
molded together or adhered together to form the frame structure of the mat.
The plastic of the
FRP pultrusions would be any one of the thermosetting plastics of the types
mentioned herein
but thermosetting polyesters and epoxies are preferred. When the frame members
are made of
wood, they can simply be bolted or riveted together. As noted herein, when
different
materials are used for the side and cross members it is also possible although
not preferred to
provide these members with an appropriate structure so that they can be bolted
together.
The encapsulating structure is provided in any way that fills in all open
spaces of the
frame structure as well as to provide the desired thickness on the top, bottom
and outer side of
the side members and the outer sides of the front and back cross members that
form the frame.
This can be done by placing the frame structure in a mold and providing the
encapsulating
material within and upon the frame as it sits in the mold.
Alternatively, the encapsulation can be provided in other ways, including but
not
limited to immersion coating of the entire core construction or by painting or
otherwise
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depositing encapsulation material to completely encapsulate the core
construction. The
encapsulating material is typically a thermoplastic polymer, a thermosetting
resin or an
elastomeric material. For example, the entire core construction can be filled
and coated with
any of these materials to form a solid unitary mat structure.
Figure 19 illustrates a variation of the invention that utilizes less plastic
or elastomeric
material to form the encapsulating structure. In this embodiment, the open
areas of frame
1000 of Figure 18 are filled with elongated members 1065 as shown in Figure
19. These
elongated members can be made of any of the materials disclosed herein,
including wood,
engineering wood, or FRP structures. Metal members can be used but these
generally are
more expensive than the other members mentioned in this paragraph and provide
more
strength that is necessary for the frame. Typically, wood members are used
with treated pine
being preferred from a cost standpoint. End grain wood sections can be
provided for greater
strength. Although these members are shown arranged to be perpendicular to the
side
members and wedged between them so that they are maintained in place during
the
application of the encapsulating material, these members can instead be
oriented parallel or
both parallel and perpendicular to the side members if desired. Also instead
of wedging the
boards in place, the can be bolted or adhered together before being bolted or
adhered to the
side members. Thus, when the encapsulating material is added it does not need
to sill in the
otherwise open spaced between the side and cross members.
Alternatively, it is also possible to use a plate, sheet or mesh upon the
upper and lower
surfaces of the cross members so that foam, particulate matter, small
particles of plastic or
rubber including rubber crumb can be added to the areas between the plate,
sheet or mesh to
fill in those areas. When a mesh is used, this generally allows the
encapsulating material to
penetrate into those areas and fill in any interstices between the particles
and form a
completely solid mat which is a preferred arrangement of the present
invention. Also, the use
of metal plate or sheet, for example, with the appropriate number of cross
members enables
the center areas of the core structure to remain open without reducing the
compression
strength of the mat. Typically, the sheeting may be plywood, plastic, metal or
composite
material, and can be attached to the mat by bolting or by an adhesive. The
sheeting and core
can be maintained in position be being encapsulated. For a more secure
attachment, holes for
the bolts can be drilled through the plate or sheeting to facilitate assembly
by allowing passage
of the bolts therethrough.
All of the mats according to the invention are to be installed on properly
prepared
ground so that they will perform acceptably. Ground preparation must be on a
uniform
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material of uniform flatness (i.e., within +/- 12" over an 8' x 14' surface).
Crushed stone or
rock no larger than 4" diameter is acceptable for preparing the ground as a
substrate for
supporting the mats.
All mats according to the invention are designed to meet the following product
specifications for preferred implementations as temporary roadways, equipment
support
surfaces, platforms and similar applications. The mats of the invention do not
cause
contamination of the ground surfaces upon which they are applied.
Preferred overall mat dimensions are approximately 8' wide x 6" tall and are
either 12
ft, 14 ft or 16 ft in length. The interlocking feature will extend the length
of the mats by about
1 ft at three locations at one end of mat. US patent 4,462,712 discloses mats
which contain
interlocking fingers and recesses which are preferred for use in the present
invention. These
are also shown in Figures 20-21 herein, wherein another preferred mat 1100 is
illustrated.
Mat 1100 is configured in the same way as mat 900 and core structure 1000 in
Figures
17 and 18 except that mat 1100 includes additional features that provide
performance benefits.
One feature is the use of the interlocking boards on the bottom surface of the
mat. These
interlocking boards 1135, 1140, 1145 are typically made of wood and are bolted
to the mat
because they provide good wear resistance but if damaged or broken, they can
be easily
removed and replaced so that the mat can continue to be used in service
without having to
provide a new encapsulated core structure.
To provide the interlocking structure, as best shown in Figure 21, recesses
are
provided on the bottom surface of the mat. These recesses 1137, 1142, 1147 are
slightly
wider than the width of the interlocking members 1135, 1140, 1145 that are to
be bolted to the
mat using bolts 1130. As shown, the interlocking members are typically boards
of wood or
other materials that are disclosed herein that have the same length as the mat
but are offset to
provide a stick out portion on one end and an open recess on the opposite end.
Thus, the stick
out portion of one mat can be received in the open recesses of an adjacent mat
so that the two
mats can be interlocked together.
The number and size of the interlocking boards is not critical to the
invention and
typically, at least two or three boards (as shown) are provided. The width of
the boards can be
between 4 and 8 inches or in some cases larger or smaller as desired depending
upon the
overall size of the mat. For an 8 foot wide mat, the use of three or four 4
inch wide boards or
alternatively three or four 8 inch wide boards would be suitable. In some
situations, a lesser
number of wider boards or greater number of less wide boards can be used. And
as noted, the
boards can be made of different materials such as wood, engineered wood, or an
FRP
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pultrusion as long as it is possible to bolt or otherwise securely attach
those boards to the mat.
Bolting of course is preferred since it will allow replacement of the boards
if they become
damaged or deteriorated during use. The bolts can be provided as an extension
from a cross
member. In particular, when the cross members are made of metal, the bolts can
be welded to
the cross member and the boards can be attached to the mat by nuts which are
secured to the
bolts after the bolts pass through the boards.
The recesses that are provided on the bottom surface of the mat are as deep as
necessary to accommodate the thickness of the boards. Typically a one or two
inch thickness
is sufficient with the recesses sized correspondingly. The recesses are not so
deep as to
contact the cross members and as noted the thickness of the encapsulation
would be at least
0.25 or 1 inch on the cross member as well as beneath the boards. Appropriate
configuration
of the cross members is needed to achieve the overall tolerances and sizes of
the mat and
encapsulating structure thickness.
Figures 20-23 also illustrate an additional feature of the invention in the
form of a
connector element 1160 that is used to mount a bumper member 1155 onto the mat
to provide
additional abuse protection to the sides of the mat. As best shown in Figures
22 and 23, the
connector element 1160 has a base portion 1162 that is attached to the side
member. When
the side member is steel, the base portion 1162 can be made of metal and
welded to the metal
side member. If the side member is made of a different material, the base
portion 1162 can be
attached by bolting, nailing or riveting. Attaching the base portion by
welding is preferred as
is the provision of all frame members to be made of a metal with steel being
the optimum
material.
Base portion 1162 includes L-shaped arm members 1164 at each end. These arm
members are received in a correspondingly shaped slots 1154 in bumper member
1155. The
bumper member 1155 is typically made of a resilient and durable plastic
material, such as
high density polyethylene so that it can withstand shock or impact as the mats
are being
moved into position or transported to a job site and installed at the
appropriate location. The
L-shaped slots 1154 of bumper member 1155 extend along the entire length of
the bumper
member. Thus, for installation, the bumper member is slid onto the side member
of the mat
with slot members 1154 for engaging arm members 1164 of connector member 1160.
End
clips, screws or bolting can be used to maintain the bumper member in position
and prevent its
unintended removal from the mat by sliding off the arm members 1164 while also
allowing
slight movement for expansion and contraction of the mat.
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Alternatively, the bumper members can be directly attached to the side members
by
bolting. Whatever type of attachment means are used it must be recognized that
the bumper
members will experience the greatest impact and abuse during movement of the
mat and for
this reason they may become damaged and require replacement. Thus, any
mechanical
connection of the bumpers to the mat must be one in which the bumpers can be
relatively
easily removed and replaced when necessary.
Figure 22 also shows the cross-section of the mat by the cut out portion on
the lower
right corner. The open space is shown as being filled by the encapsulating
material 1105 but
that the space is relatively large and requires quite a bit of material to be
filled into those open
spaces of the mat. This is why the construction of Figure 19 is preferred
since the inclusion of
additional members or filler into those spaces greatly reduces the amount of
plastic or
elastomeric material that would be needed to form the encapsulating structure.
Figure 22 also shows that the connector element 1160 can be welded to the side
member prior to encapsulation of the frame. In doing this however the
encapsulating material
is molded so that it does not extend over the arm members 1164 of connector
element 1160 as
those need to be exposed to receive bumper element 1155.
Figure 23 also shows the drainage channels 1125 that allow water to drain from
the
mat during use.
In certain specific applications, the upper surface and possibly the lower
surface of the
encapsulation structure can require additional layers for further extending
the service life of
the mat. To attach these additional layers, the cross and side members can be
provided with
appropriate bolting that extends through the encapsulating structure and
allows attachments of
the additional layers.
These optional additional layers generally include two (2) layers of
individual wood or
composite boards, having cross section dimensions of 1.75" by 8". These can
both be on the
top side of the mat or one layer can be on the top side and one on the bottom
side so that the
additional layers form the outer layers of the mat. The members of the
additional layers
would generally be joined together by bolting, nailing or riveting if made of
wood or by other
attachment means such as adhesives if made of FRP. They are also attached to
the mat in a
way that facilitates their replacement if damaged during use, with bolting
again being the
preferred method of attachment.
In another alternative embodiment, each board of the various layers of the mat
are
encapsulated with the material or a coating of one or more of the various
materials mentioned
herein. The encapsulation can be provided in other ways, including but not
limited to
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immersion coating of each board or by painting or otherwise depositing
encapsulation
material to completely encapsulate the boards. Combinations of these
techniques can be used
as well, wherein a sheet or layer of the material is initially applied to the
boards. Thereafter,
the ends of the boards can be sealed with coating material and the overlapping
edges of the
sheet or layer sealed with an adhesive. Polymer sleeves can also be used with
the ends of the
sleeved folded upon the ends of the boards. Thus, each board will be protected
from moisture
as well as from abrasion due to traffic or equipment that passes over or is
placed upon the mat.
The outermost layers experience the greatest traffic and for that reason may
be further
provided with an additional surface coating of a material that provides
additional abrasion
resistance or with particles of various materials such as inorganic, rubber or
plastic material to
provide a non-slip surface. Crumb rubber can be used for this purpose. For
environmental
benefits, the crumb rubber can be obtained by grinding used automobile tires
into the desired
particulate size.
The provision of a encapsulation on the boards of the central layer protects
that layer
from moisture which would cause rotting or deterioration of the boards This
also enables the
central layer to be reused if the boards of the outer layers require
replacement.
When assembling the encapsulated boards into the mat, care should be used to
close
off any holes made for bolts or other attachment means. Bolts can be made of
stainless steel
or aluminum to prevent rusting while the holes through which they pass can be
sealed off with
a rubber gasket or o-ring placed beneath the bolt heads or nuts to make it
more difficult for
moisture to enter into the wood through the bolt holes.
And while offsetting of certain boards is shown for providing an interlocking
with
adjacent mats, this is not always needed such that interlocking can be
considered to be an
optional yet desirable feature. Interlocking is often preferred to avoid
staking of the mats to
the ground or to avoid including other more complex components for use in
connecting
adjacent mats together.
Another feature of the invention is the use of color coding to identify the
core
construction of the mat. As the encapsulation is opaque, it is not possible to
visually
determine how the core is made. Thus, a color coding system can be used to
identify the
specific core construction. This can also be used to identify mats for a
particular customer or
end user. When mats are rented or leased, the color coding can be used to
identify which mats
belong to the leasing company compared to mats provided by others. The color
coding can be
of a single color or of certain stripes, patterns, dots or other indicia that
provides a "signature"
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that identifies the specific core that is present in the mat or a particular
end user or owner of
the mat.
All of the mats according to the invention are to be installed on a prepared
ground
surface so that they will perform acceptably. Ground preparation is typically
upon a material
of uniform flatness (e.g., within +/- 12" over an 8' x 14' surface). Crushed
stone or rock
generally no larger than 4" diameter is acceptable for preparing the ground as
a substrate for
supporting the mats.
All mats according to the invention that include the most preferred core
construction or
alternatives thereof are designed to meet the following product specifications
for preferred
implementations as temporary roadways, equipment support surfaces, platforms
and similar
applications. A further benefit of the mats of the invention is that they do
not cause
contamination of the ground surfaces upon which they are applied.
Preferred overall mat dimensions are approximately 8' wide x 6" tall and are
either 12
ft., 14 ft. or 16 ft. in length. The interlocking feature will extend the
length of the mats by
about lft at three locations at one end of mat US patent 4,462,712 discloses
mats which
contain interlocking fingers and recesses which are preferred for use in the
present invention.
The mats typically include three (3) layers of individual wood or composite
boards,
having cross section dimensions of 1.75" by 8".
The spacing between individual boards or components in the upper layer is
preferably
approximately 1.25" to allow water to drain from the mat. The slip resistance
of the mat is
improved by the draining of the excess water, especially when use in locations
that experience
heavy rain or snow conditions.
The preferred mats have physical properties that meet or exceed the physical
properties of a conventional white oak mat.
The mat must also provide sufficient load bearing capacity: a fully supported
mat (one
that is properly installed on an approved ground surface preparation) must
withstand a 10 ton
load, spread over a 12" diameter surface without degradation of mat properties
or permanent
deformation of core construction of the mat. The core would have a crush
resistance of
between about 600 and 800 psi depending upon the application. This provides
resistance
against compression while not detracting from providing resistance to torsion
forces that
applied to the mat by vehicles passing thereover.
Optionally and preferably, the perimeter edges of the mat are provided with
additional
protection to prevent or reduce damage to the core construction of the mat
from side entrance
or egress onto the mat from large vehicles with steel tracks. The edge
material helps protect
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the core construction and may be removable. The edge material may be made of
wood, metal,
or a plastic or elastomeric material.
Preferably, the encapsulation is relatively non-flammable. Flammability of mat
is
defined as Class 2 (B) flame spread when measured by ASTM E84 test criteria.
The
flammability properties of the encapsulation materials can be enhanced by
adding the
appropriate conventional flame retardant or other additives that are known to
impart such
properties.
The encapsulation should also allow dissipation of static electricity. For
this purpose,
the encapsulation can include carbon black, metal particles or other
conductive fillers.
To prevent premature deterioration of the encapsulation, the material for the
encapsulation should contain UV inhibitors as necessary and in an amount
sufficient to reduce
deterioration of physical properties or color.
To assist in gripping of vehicle or personnel traffic on the mat, a non-slip
or textured
surface can be applied to the exposed surface of the encapsulation This can be
sand or other
grit material that is embedded in the encapsulation during preparation or
molding or that is
later added with an adhesive or a coating.
Alternatively, the provision of a plurality of channels or grooves in the
encapsulation
on both the top and bottom surfaces of the mat can be used to provide traction
to objects
moving on the top surface of the mat and to provide resistance to slipping
when the bottom
surface of the mat is placed on wet or muddy ground surfaces.
For ease in moving of the mats, attachment points can be provided that allow
for
lifting and handling of individual mats. Lifting hardware preferably includes
D rings, 0-rings,
chain, or cables at 2-4 locations on the upper surface of the mat. The exact
position and
attachment of lifting hardware is designed based on the size and weight of the
mat and is
intended to avoid damage to the encapsulation or the internal structure of the
mat.
The core construction of the mat preferably is not hollow. If hollow
components are
used for the various layers of the core construction, such as metal lath,
metal sheets with
openings provided therein, thermoplastic or fiberglass reinforced
thermosetting plastic
structures with open or closed cells, or the like, the openings or cells may
preferably be filled
with a non-absorbent material. A wide variety of different plastic,
elastomeric or foam
materials can be used for this purpose. The hollow portions can be used as is
or can be
provided with filler or other materials to increase or decrease weight as
needed. Fillers of
glass, ceramic or metal particles can be included to provide additional weight
or strength to
the mat. Other materials such as recycled rubber tire material or other
environmentally
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friendly materials can instead be used. Preferably, the mat has a weight that
is on the order of
a white oak mat of similar size.
For a more advanced product, the core construction layer may be made of
environmentally resistant material to further prevent against degradation due
to weather
conditions in the event that the encapsulation becomes damaged or otherwise
compromised to
allow liquid to enter into the core construction.
The term "environmentally resistant material" means a material that is not
subject to
deterioration by water, moisture or other environmental conditions when
compared to a
conventional wood material such as white oak that is commonly used for such
mats. This
term includes thermoplastic and thermosetting materials as disclosed herein
along with
elastomers and even metals such as steel, aluminum or stainless steel. While
steel does rust
when encountering moisture or water, this is not considered to be a
deterioration of the
material as it is a surface phenomenon that does not affect the physical
properties of the
material but instead just detracts from its surface appearance. To avoid this,
the steel
components can be coated or painted to provide a better appearance and even
further
environmental resistance. Under certain conditions treated wood can withstand
rotting and
degradation much better than untreated wood such that it would be considered
to be an
environmentally resistant material because of it improved resistance against
rotting.
A number of additional features may be provided in the mats of the present
invention.
A radio frequency identification (RFID) tag can be embedded into the access
mats in a
routered pocket in the core construction to enable the access mats to be
monitored in an
inventory system or when rented for use. The tag provides a unique
identification serial
number for each mat, such that the mats which are being used or rented can be
tracked and
accounted for as to location of use. The mats can be scanned when in a
warehouse, when
loaded on trucks for delivery, when delivered to a job site, or when collected
from a jobsite
after use. The RFID tags can be active or passive and if desired, other
tracking devices such
as barcodes could similarly be for the same purposes. It is preferred,
however, that the RFID
tag be embedded in the mat so that it is protected from damage by the
encapsulation. When a
barcode or other surface mounted tag or indicia is used, it should be placed
on a surface
portion of the mat that is less likely to experience wear or abuse. Thus, the
tag may preferably
be applied onto the side of the mat so that it is not directed exposed to
traffic on the mat.
In order to manipulate the mats for loading/unloading, or moving from one
location to
another or for installation and retrieval, the mats can include a retractable
lifting element.
This can be the lifting elements described above and those elements lie in a
recess in the top
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surface of the mat during use for ease of access and to prevent tripping or
damage to items
moving over the mat or damage to the lifting elements themselves.
Alternatively, a more
complicated design such as that of US patent publication 2008/0292397 can be
used.
To assist in the use of the mat during the night or on days that are dark due
to poor
weather conditions, the mat may include one or more lighting elements, such as
those
disclosed in International application WO 2006/048654. These lighting elements
would
preferably be embedded in the encapsulation. The encapsulation can be provided
of clear
plastic, so that the lighting element may be positioned below the
encapsulation for better
protection of the lighting element during use. As the embedding of the
lighting element below
the encapsulation surface can result in reduced luminosity, a skilled artisan
can best determine
the appropriate location for the placement of the lighting element in or under
the
encapsulation and for providing the encapsulation of the appropriate color or
clarity to achieve
the desired lighting brightness. This can also be adjusted by providing a
larger number of
lighting elements or of lighting elements of larger size.
The present invention provides unexpected benefits over the art in that the
encapsulation provides resistance to abrasion and abuse of the core
construction while also
preventing moisture, water or chemicals from the surrounding environment from
penetrating
into the core construction. Additionally, the mats have anti-static properties
and provide
traction and anti-skid surfaces depending upon the finish of the encapsulation
or coating
surfaces that are exposed. These can be provided with particulate matter of
any type of
inorganic particles or plastic or rubber pellets to provide an anti-skid
surface. The amount of
particles would depend upon the size and can be determined by routine testing
depending
upon the material use for the encapsulation or coating. Also, certain
materials such as rubber,
when present as or in the encapsulation, act as a heat sink to allow ice to
melt more quickly
from the mat which is a safety feature when the mats experience snow and ice
conditions in
winter. The mats can also be pigmented to be place to assist in absorbing
sunlight to melt ice
or snow.
All of these features contribute to the ability of the mat to provide a much
longer
service life compared to when wood components are used alone since the
encapsulation
prevents rotting or other chemical degradation of the wood components of the
core
construction. Further enhancements in service life can be expected by
providing a core
construction made of thermosetting or thermoplastic materials or plastic
coated metal.
Finally, when the service life of the encapsulation is being approached, the
encapsulation can
be cut off or otherwise removed from the core so that a new encapsulation can
be applied.
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CA 02980897 2017-09-25
WO 2016/153734 PCT/US2016/020081
Alternatively, when single boards are encapsulated, only those where the
coating or
encapsulation is damaged need replacement. To the extent that any of the
components of the
upper or lower layers are damaged, they can be replaced so that a new mat can
be made with
the reuse of a substantial part of the core construction. In some situations,
such as where the
core construction remains in relatively good condition from, e.g., the use of
non-wood core
components, only a portion of the encapsulation can be removed and replaced,
thus providing
further savings in recycling rather than replacing the mat.
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