Note: Descriptions are shown in the official language in which they were submitted.
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MAT CONSTRUCTION WITH ENVIRONMENTALLY RESISTANT CORE
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.
Also, conventional crane mats that are typically 4 feet wide and utilize 8x8
inch to
12x12 inch beams that are up to 40 feet in length, utilize beams that are made
of oak and
preferably white oak as that material provides acceptable performance of the
mats for a
significant service life at a reasonable cost. Such mats are also available
from Quality Mat
Company, Beaumont, Texas. These mats, which are often called timber mats or
crane mats,
typically utilize virgin wood utilize virgin wood that is shaped and cut to
length to meet
design demands. Due to weather conditions and other environmental factors,
however, the
availability of trees that can be harvested to make such large size and length
beams is
reduced, thus making it difficult to obtain suitable quantities to make large
numbers of mats.
Accordingly, alternatives are needed for crane mat constructions to conserve
the
amount of wood beams that need to be included. Also, the materials that may be
considered
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as alternatives need to possess the necessary physical properties to be able
to withstand harsh
outdoor conditions as well as to support heavy equipment. And of course cost
is a factor in
determining the selection of alternate materials, as it is not cost-effective
to provide a mat
that is multiple times more expensive than one that can be made of wood.
Thus, there is a need for improvement in these types of mat constructions both
to
provide longer service lives as well as to conserve natural resources, and
these needs are
now satisfied by the industrial mats of the present invention.
SUMMARY OF THE INVENTION
The invention now provides a mat that includes a core structure that provides
strength and rigidity to the mat. The core structure is provided as one or
more components
comprising a sheet, a plurality of elongated members, a frame, a plurality of
compartments,
or combinations thereof. These components of the core structure are made of
environmentally resistant non-wood materials. The mat also includes at least
one outer layer
attached to the core structure directly or indirectly through other
components, with the outer
layer(s) having a length and width that substantially corresponds to that of
the core structure
and that forms an upper or lower surface of the mat or both upper and lower
surfaces of the
mat. The at least one outer layer comprises a plurality of elongated members,
wherein the
elongated members of the outer layer(s) are made of wood, engineered wood,
thermoplastic,
thermosetting plastic or elastomeric materials, with the materials of the
elongated members
of at least one outer layer being different from the materials of the
structural components of
the core. Thus, the components of the outer layer(s) provide abrasion, wear
and abuse
resistance to the mat and are removably attached to the core construction so
that the
components of the outer layer(s) are replaceable when damaged while the core
structure is
protected and not subject to degradation so that it can be reused to form a
mat having
replaced components in the outer layer(s).
The environmentally resistant materials for the structural components of the
core
structure may be selected from treated wood, metal, an elastomeric material, a
thermoplastic
material, a thermosetting material or a combination thereof The core structure
is an
essential component to the mat which is designed to provide sufficient
strength and rigidity
to the mat, both initially and after the mat has been in service for a while,
as the
environmentally resistant material can withstand repeated contact with rain
and snow
conditions without degradation or deterioration.
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One outer layer forms the upper surface of the mat, while and another outer
layer
forms the lower surface of the mat. Optionally, additional layers comprising
one or more
components in the form of a sheet, a plurality of elongated members or
combinations thereof
can be present for attaching the outer layer(s) to the core structure.
Preferably, the outer
layer(s) are removably attached directly or indirectly to the core structure
by bolting. The
components of the outer layer(s) typically have a modulus of about 1.6 M psi.
In a preferred arrangement, the structural components of the core structure
include
elongated members of a thermoplastic or thermosetting plastic material, a
solid or apertured
plate or sheet (i.e., one containing a random or ordered set of openings or
holes therein) of a
thermoplastic or thermosetting plastic material, and two outer layers are
provided: one outer
layer comprising a plurality of elongated members of wood or engineered wood
and forming
the upper surface of the mat and another outer layer forming the lower surface
of the mat and
comprising a thermoplastic, thermosetting plastic or elastomeric material in
the form of
elongated members, a solid or apertured plate or sheet structure, or a grid or
grating, the
latter two being specific embodiments of an aperture plate or sheet structure.
Another embodiment of the invention relates to a method for prolonging the
service
life of an industrial mat that has wood components. This method includes
configuring the
industrial mat to have a core structure that provides strength and rigidity to
the mat, wherein
the core structure is provided as one or more structural components comprising
a sheet, a
plurality of elongated members, a frame, a plurality of compartments, or
combinations
thereof and wherein the components of the core structure are made of
environmentally
resistant non-wood materials; providing at least one removable outer layer
attached to the
core structure directly or indirectly through other components, with the outer
layer(s)
forming an upper or lower surface of the mat or both upper and lower surfaces
of the mat,
wherein the at least one removable outer layer comprises elongated members
made of wood,
engineered wood, thermoplastic, thermosetting plastic or elastomeric materials
to provide
abrasion, wear and abuse resistance to the mat, with the materials of the
elongated members
of at least one outer layer being different from the materials of the
structural components of
the core structure. The method then includes renewing the mat by replacing
elongated
members of the outer layer(s) that are damaged or deteriorated during use by
removing one
or more of the damaged or deteriorated elongated members while reusing the
core structure
that is protected and not subject to degradation to form a renewed mat having
replaced
elongated members or other components in the outer layer(s).
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In this method, the components of the outer layer(s) can be attached to the
mat by a
bolting arrangement so that they are removable by loosening the bolting
arrangement. Next,
the replacement components are attached to the core structure using the same
bolting
arrangement.
Additionally, the mats can be provided with beams or bumper members made of
wood or a plastic material upon the longitudinal sides of the core structure
to protect the core
structure from damage due to transport or installation of the mat, with the
beams or bumper
members optionally also provided on the ends of the core structure. The beams
or bumper
members can also be configured to be removably attachable to the core
structure so that they
are replaceable when damaged to form a renewed mat having replaced beams or
bumper
members.
The mats of the invention are typically designed to provide sufficient load
bearing
capacity: A fully supported mat (one that is properly installed on a suitable
prepared ground
surface) must be able to withstand a 10 ton load, spread over a 12 inch
diameter surface
without degradation of mat properties or permanent deformation of the mat. The
support
structure would have a crush resistance of between about 500 and 800 psi to as
much as
1000 psi depending upon the specific construction of the support structure and
when
properly installed on a suitably prepared ground surface. This provides
resistance against
compression as large vehicles or equipment move over or are placed upon the
mat and
avoids permanently deforming the core structure.
The core structure may be any of a plurality of elongated tubular members made
of
metal, a thermoplastic material or a thermosetting material with each tubular
member being
of the same or a different material, being hollow or solid or being individual
members or
joined together to form a unitary component. The thermoplastic, thermosetting,
elastomeric
or polyolefin material may be present as a sheet or in a solid or honeycomb
structure. The
honeycomb structure may have closed or open cells. The cells of the honeycomb
structure
optionally may be provided with a filler material to increase the weight of
the mat, as well as
to control, preclude or provide absorption of liquids. If necessary, when the
open cells of the
core structure are to be provided with filler material, upper and lower sheets
can be included
to assist in retaining the filler material in the cells.
Another embodiment of the invention relates to a crane mat having top and
bottom
surfaces and comprising first and second side beams having top, side, and
bottom surfaces; a
non-wood support structure located between and connecting the first and second
side beams;
a plurality of j oining rods that attach the side beams to the support
structure, with the joining
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rods passing through the sides of the beams and support structure; and a first
plurality of
elongated members attached to the upper portion of the support structure. The
support
structure has upper, lower and side portions, a height that is less than that
of the side beams,
a width and a length, with the first and second longitudinal members being
joined together
by a plurality of cross members.
The top surface of the mat is substantially flat and is formed by the top
surfaces of
the beams, the first plurality of elongated members, or both. The mat may
include a second
plurality of elongated members attached to the lower portion of the support
structure. The
bottom surface of the mat can be substantially flat, being formed by the
bottom surfaces of
the beams, the second plurality of elongated members, or both.
The joining rods typically comprise bolts that pass through the side beams and
support core. Preferably, the beams and longitudinal members include tubular
sleeves that
facilitate passage of the bolts therethrough for assembly of the mat. The
first and second
plurality of elongated members typically have the same thickness, with the
joining rods each
preferably comprising a carriage bolt and nut arrangement wherein the bolts
pass through the
sleeves in a central area of the side beams and the longitudinal members of
the support
structure and are secured in place by the nuts.
The beams generally have width and height dimensions of between about 1x6
inches
and about 24x24 inches or between about 6x6 inches and about 16x16 inches; the
first and
second longitudinal members are joined together by cross members spaced about
10 to about
inches apart; the joining rods are spaced about 3 to about 6 feet apart; and
the mat has a
width of between about 4 and about 8 feet and a length of between about 4 and
about 60 feet.
In a preferred embodiment, the side beams may be made of solid cut wood,
engineered lumber or a thermosetting plastic, with the first and second
longitudinal members
25 configured as a flat plate, I-beam or rectangular or C-shaped beams for
contact with the side
beams. The cross members may be configured as a flat plate, and I-beam or a C-
shaped
beam, while the plurality of elongated members are boards made of solid cut
wood,
engineered lumber or a thermosetting plastic. The elongated members are bolted
to the
support structure.
30 The
first and second longitudinal members and plurality of cross members of the
support structure typically form a frame, with the mat having a width of
between 4 and 8
feet; and the support structure has a width that is about 2 to 8 times the
width of one side
beam with the mat having a width of about 4 to 12 times the width of one side
beam.
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The side beams generally have the same dimensions and are attached to the
support
structure to locate their upper surfaces about 1.5 to 3 inches above the
support structure and
to locate their lower surfaces about 1.5 to 3 inches below the support
structure, wherein the
first and second plurality of elongated members have a thickness of about 1.5
to 3 inches to
provide the substantially flat upper and lower surfaces to the mat.
To provide an interlocked structure of conjoined adjacent mats, the first side
beam of
the mat is sized to provide about one half the height of the mat, with the
first side beam
attached to an upper portion of the support structure. Alternatively or
additionally, the
second side beam may be sized to provide one half the height of the mat and is
attached to
the second side of the support structure in a lower position. To stabilize
certain of these
mats, an additional first beam of the same dimensions as the first beam is
provided for
placement below the first side beam of the first mat and an additional second
side beam of
the same dimensions as the second beam is provided for placement upon the
second side
beam of another mat to provide the substantially flat upper and lower surfaces
of the
conjoined structure and to stabilize the outermost sides of the conjoined
structure.
Yet another embodiment of the invention relates to a mat comprising a support
structure in the form of a frame or ladder structure having longitudinal and
end sides, with
the support structure configured to support or allow attachment of other
components to form
the mat. The mat includes additional layers of elongated members attached
above, below or
both above and below the support structure for forming an upper surface, lower
surface or
both upper and lower surfaces of the mat. The mat also includes bumper members
removably attached at least to the longitudinal sides of the frame or ladder
structure to
protect against damage due to side impact during transport or installation of
the mat. The
bumpers are made of a plastic or elastomeric material and have a shape that
provides an
outer surface that extends beyond the sides of the support structure and has
sufficient
compression to absorb impact and shock to protect the support structure. The
bumper
members are removable so that they can be replaced when damaged so that the
support
structure and upper and lower layers of elongated members can be reused.
Additionally, the
upper and lower layers of elongated members can also be replaced when
necessary, while
the environmentally resistant support structure can be reused.
The longitudinal sides of the support structure may include an I-beam having
an
outer side facing open cavity, with the bumpers that are attached to the I-
beam fitting in the
I-beam cavity. Alternatively, the longitudinal sides of the support structure
can include a
beam having a flat outer side surface, with the bumpers are positioned
adjacent the
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longitudinal sides by additional members or lips that retain the bumpers in
place against the
flat outer side surface of the beam. Other bumper embodiments are disclosed
herein.
In another preferred embodiment, the support structure is made of steel or
hollow,
filled hollow or solid rectangular tube members of fiberglass reinforced
thermosetting plastic
__ material, and the elongated members are made of wood, engineered wood or a
thermoplastic
or thermosetting plastic material. Also, open areas of the support structure
can be provided
with one or combinations of: wood boards that provide greater weight,
compressive strength
or ruggedness to the mat, wherein the core of wood boards are configured to
fit within
openings of the support structure and are bolted together so that they do not
move around
__ inside of the mat; recycled rubber tire material, sand or other particulate
or solid filler
material located in open areas of the support structure, wherein the
particulate filler material
is retained in place in the support structure by a mesh, screen or sheets that
are secured to the
top and bottom of the support structure; or foam or extruded polymer material
located in
open areas of the support structure.
To protect the mat from damage due to transport or installation, the mat may
include
protective members upon at least the longitudinal sides of the core structure
to protect the
core structure from damage due to transport or installation of the mat. These
protective
members may be beams or bumpers made of wood or a plastic material and they
may also be
provided on the front and rear ends of the core structure.
When protective members are provided, a preferred may embodiment includes a
frame configured to support and provide a periphery about the core mat; upper
and lower
layers protecting upper and lower surfaces of the core. Advantageously, the
frame
comprises steel I-beams and the bumpers are received in outer cavities of the
I-beams.
Alternatively, the frame is a box frame made out of a rectangular tube member
of fiberglass
__ reinforced plastic and the bumpers sit on the outer side of each box frame
member. The
bumpers may extend onto the top and bottom surfaces of the mat. Alternatively,
the
bumpers are held in position by lip members associated with the upper and
lower layers of
the mat. If desired, the lip members may be integral with the upper and lower
layers of the
mat.
The bumpers are generally configured to have a narrower upper and lower
profiles
and a wider central profile to accommodate attachment to the mat, with the
upper and lower
layers being made of a plastic or elastomeric material. If desired, the box
frame members
may be filled with an insert, e.g., a molded solid, foam or pellet material.
For simplicity, the
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box frame structure is protected by an outwardly adjacently positioned wood
structure. The
core may be a molded solid or foam material, or can be made of oak.
For lifting and movement of the mats when the support structure comprises
steel
members, lifting elements comprising D-shaped rings, 0-shaped rings, chains,
or cables that
are connected directly to the steel members are provided to allow overhead
lifting of the mat.
And to improve the environmental resistance of the mat, the steel members of
the support
structure may be coated or painted.
Finally, the mats may include one or more of a radio frequency identification
(RFID)
tag to enable the mat to be monitored in an inventory system or when rented
for use; lighting
elements embedded in the elongated members to provide light to assist in the
use of the mat
during the night or on days that are dark due to poor weather conditions; or
color coding to
identify the construction of the mat or to identify mats for a particular
customer, end use or
to indicate that the mat is rented or leased.
BRIEF DESCRIPTION OF THE DRAWINGS
The appended drawing figures provide additional details of the invention,
wherein:
Figure 1 is an exploded view of one embodiment of the mat of the invention
which
includes a core structure of fiberglass reinforced polyester beams and outer
wood board
layers;
Figure 2 is a side view of a reinforced polyester beam for use in the mat of
Figure 1;
Figure 3 is a view of the assembled mat of Figure 1;
Figure 4 is a perspective view of another embodiment of the mat of the
invention to
illustrate an open celled honeycomb structure for the core;
Figure 5 is a perspective view of another embodiment of the mat of the
invention to
illustrate an open celled hexagonal honeycomb structure for the core structure
and the
presence of additional sheet members to retain particulate filler in the
cells;
Figure 6 is an exploded view of a mat that includes a steel I-beam frame, wood
skins,
a foam core structure and bumpers on all sides of the mat;
Figure 7 is an exploded view of a mat that includes a steel I-beam frame,
polymer
skins, a foam core, and bumpers on all sides of the mat;
Figures 8 and 9 are exploded views of a mat that includes a fiberglass
reinforced tube
section frame, polymer skins, a foam core structure that interlocks with the
skins and
bumpers on all sides of the mat;
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Figure 10 is an exploded view of a mat that includes a fiberglass reinforced
tube
section frame, wood boards, a laminated oak core structure and an outer oak
edge
construction that protects the tube section;
Figure 11 is an exploded view of a mat that includes a metal frame, upper and
lower
wood boards and wood bumpers;
Figure 12 is a perspective view of another embodiment of a mat according to
the
present invention;
Figure 13 is an exploded view of the mat of Figure 12 to illustrate the
various
components present therein;
Figure 14 is a perspective view of the support structure for the mat of Figure
12;
Figure 15 is a perspective view of yet another embodiment of a mat according
to the
present invention;
Figure 16 is a partial sectional view of the support structure for the mat of
Figure 15;
Figure 17 is a view of certain peripheral components for the mat of Figure 12;
Figure 18 is a perspective view of a crane or pipeline mat according to the
present
invention;
Figure 19 is an exploded view of the crane or pipeline mat of Figure 18;
Figure 20 is an exploded view of an interlocking mat having a steel frame and
woodblock core;
Figure 21 is a view of the constructed mat of Figure 20 with a portion of the
corner
removed to show the welded frame and core structure;
Figure 22 is an exploded view of an interlocking mat having a grating of a
fiberglass
reinforced thermosetting material; and
Figure 23, illustrates the assembled mat of Figure 22.
DETAILED DESCRIPTION OF THE INVENTION
The present invention now provides an improved mat that possesses better
environmental resistance due to the provision of a core structure made of
environmentally
resistant materials. 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
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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 its improved resistance
against rotting.
The invention provides a number of different mats each having an
environmentally
resistant core and that includes replaceable elongated members, such as wood,
plastic or
elastomeric boards, on the top and/or bottom surfaces of the mat. These
members can be
replaced as they wear or are damaged while the environmentally resistant core
can be reused
and provided with new elongated members. The core is typically made of steel
components,
thermoplastic members, thermoplastic units, and thermoset gratings.
The new and improved industrial mats of the present invention now provide
additional advantages over conventional mats. For one, the use of a support
structure that is
not made of wood conserves timber resources which would otherwise be harvested
to
provide the long length beans for construction of the mats. Now, at most, only
the side
beams of wood are used with the support structure providing the remaining
width of the mat.
And in the preferred arrangements, the support structure is not of the same
height as the side
beams to allow other, thinner elongated members to be applied to the top and
bottom of the
support structure so that the upper and lower surfaces of the mat are
substantially uniform.
These members may be wood but shorter lengths and thinner cross sections are
used.
The wood members of the mat are preferably made of hardwoods such as white
oak,
red oak, beech, hickory, pecan, ash or combinations thereof. Also, engineered
wood
materials as described herein can instead be used. Treated pine can be used as
a filler
material because it is a lower cost, readily available wood material.
For other embodiments, the use of fiberglass reinforced thermosetting resins,
generally in the form of a pultrusion, for the side beams and elongated
members essentially
eliminates the use of any wood as structural components in the core structure
of the mats.
This further conserves timber resources. As noted herein, wood or other
materials can be
used as filler in the core structure if necessary or desired to recycle
materials that would
otherwise need to be discarded as scrap because those components are solely
used to provide
weight rather than strength to the mat.
The term "fiberglass reinforced thermosetting plastic material" or "fiberglass
reinforced plastic" means a thermosetting material that is reinforced
generally with glass
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fibers or other types of fiber strengthening materials, such as carbon,
aramid, basalt or other
fiber materials. The thermosetting material is usually a polyester, epoxy,
vinylester or even
a phenol formaldehyde resin. Skilled artisans are well aware of these and
equivalent
materials that are suitable to meet this definition.
The use of a non-wood support structure enables that component to be reused in
the
event that the side beams or elongated members become damaged or experience
deterioration due to use and exposure to harsh environmental conditions. By
being made of
more robust and environmentally resistant materials, it is possible to
disconnect the joining
rods to take apart the mats and remove the damaged side beams or elongated
members, and
then add new components to the structure to form a new mat. In effect, this
reduces the
demand for wood beams or elongated members by 50 to as much as 100%.
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 inches to 24x24 inches with lengths from about
4 feet to as
much as 40 feet or more. Preferred dimensions are described throughout the
specification.
As noted, previous and current mats of this type that are commercially
available are
primarily constructed of monolithic wood.
The term "non-wood" to describe the support structure is used for its ordinary
meaning. The components of the structure are generally not made of wood but
instead are
made of metal, a thermosetting plastic or other materials that are resistant
to degradation due
to environmental factors such as moisture from water, snow or ice, organisms
that can cause
wood rot, or similar external factors that affect 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 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.
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Additionally, all dimensions recited herein are approximate and can vary by as
much
as 10 % to in some case 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.
The invention contemplates the use of various components in the mat structure.
Typically, elongated members of wood boards have been used and the term
"elongated
members" as used herein means structures that assimilate wood boards or are
otherwise
configured with rectangular cross sections and lengths which are preferably
the full length of
the mat. Shorter lengths of these structures can be used, however, as they are
typically
bolted to the other components to form the mat. These elongated members are
typically
solid but they can be hollow tubular components which are optionally filled
with other
materials such as foams or particles. The sizes for such elongated members are
about 1 to 4
inches thick, about 6 to 12 inches wide and typically the length of the mat.
Shorter boards
can be used if desired and often are used when the mat is longer than 20 feet
but full length
boards for the entire length of the mat is preferred when possible. Lengths of
12 to 16 feet
are common. For solid members, the preferred dimensions are 2 inches thick, 8
inches wide
and a length that is the same as that of the mat (e.g., often 12, 14 or 16
feet or longer if
desired).
Other embodiments utilize components in the form of a structured unit. This
can be
a sheet or plate, or a layer which is solid or that includes cells or other
openings to reduce
weight or provide openings to facilitate joining of the components by bolting
or permanent
or other non-permanent means. Typically, the size of such units ranges from
about 1 to 4
inches thick, about 4 to 12 feet wide and typically the length of the mat. It
is also possible to
use multiple units in large mats, such as units that represent a portion
(e.g., 1/3 or 1/2) of the
size of the mat. The preferred dimensions are about 2 to 4 inches thick, 8
feet wide and a
length that is the same as that of the mat (e.g., often 12, 14 or 16 feet or
longer if desired).
Typically bolting is used as it allowed the components of the outer layers of
the mat
to be removed if damaged or deteriorated and replaced with other components
while the
environmentally resistant core of the mat can be reused. For certain mats,
some or all of the
components that are used can be permanently joined together by welding or an
adhesive.
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A wide range of thermoplastic or polymeric materials can be used for the core
structure of the mats of this invention. These materials would be molded or
cast to the
desired size and thickness of the mat. Useful 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 (PAT)
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)
Polyetherketoneketone (PEKK)
Polyetherimide (PEI)
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Polyethersulfone (PES)
Polyethylenechlorinates (PEC)
Polyimide (PI)
Polylactic acid (PLA)
Polymethylpentene (PMP)
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)
It is also possible to utilize fiberboard as the elongated members or sheets
that form
the core structure. The fiberboard material is made of recycled plastic or
polymeric
materials from used carpets, plastic packaging and the like. They can be
provided in the
desired sizes for use as the core structure of the mats of this invention. In
addition to being
environmentally resistant due to their plastic content, these fiber boards are
environmentally
friendly by allowing recycling of used materials that contain plastic or
polymeric materials.
The core structure may also be made of an elastomeric material. The elastomers
are
usually thermosets (requiring vulcanization) but may also be thermoplastic.
Typical
elastomers 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;
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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 (i.e., 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, thermoplastic or thermosetting materials disclosed herein 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. Also, when the entire mat is made of
elastomeric,
thermoplastic or thermosetting materials, the entire mat can be made as an
integral
component.
The polymeric or elastomeric core structure can be made as a flat sheet
provided that
it has the necessary weight and rigidity. These variables can be controlled by
the selection
of the particular polymer or by providing a particular configuration for the
core. For
example, the core structure can be made with a honeycomb or open cell
structure.
The term "honeycomb structure" refers to a structure that has openings or open
cells
therein which can be used to reduce weight or can be filled with other
materials. The shape
of the cells can be hexagonal, square, rectangular, or of another polygonal
shape, or they can
even be round. The cells can be adjacent to each other or spaced as desired
and can extend
in either the horizontal or vertical or direction.
With this construction, the weight of the mat can be increased and the
resistance to
liquid absorption improved by filling the cells of the honeycomb structure of
the core
structure with one or more of various materials, including sand, dirt, gravel,
particles of
plastics, ceramics, glass or other materials, various foam materials, or even
of recycled
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materials such as particles of ground vehicle tires or other recyclable
materials. The latter
are preferred to fill the core structure to provide an environmentally
friendly or "green" mat.
The plastic core structure can also be provided in two half sections in the
vertical
direction, i.e., an upper section and a lower section. The upper section can
be designed with
protrusions or raised and lower areas on its lower surface with the lower
section designed
with complementary recesses or lower and raised areas on the surface that
faces the upper
section so that the upper and lower section can be joined together by
engagement of the
protrusions and recesses or raised and lower areas.
Alternatively, the core structure can be made of a metal frame or ladder
structure.
Typically, steel, stainless steel or aluminum are used and the frame or
structure can be
bolted, riveted or welded together. The metal frame or structure if made of
steel can be
further protected by galvanizing, painting or otherwise depositing powder or
liquid coating
material thereon to prevent moisture from contacting the steel. For example,
the entire core
structure when made of steel can be coated with a paint or even with a
thermoplastic or
thermosetting resin.
The metal frame or ladder structure can be used as is or can be configured
with
netting, mesh or other material that allows any frame openings to be provided
with a filler to
modify the weight of the mat. If additional weight is desired, heavier filler
material can be
used. To fill in the interior sections of the frame without adding too much
weight to the mat,
a plastic or rubber filler of low density particles or foam can be used.
The assembled mat in the preferred embodiments can vary depending upon the
specific type of mat. 2-ply or 3-ply laminated mats will typically include
elongated
members that are about 2x8 inches with the mat having a width of approximately
8 feet and
a length of about 12, 14 or 16 feet. General industrial mats would typically
have a thickness
of approximately 6 inches which is made up of a core construction that is 2 or
4 inches thick,
an upper layer that is 2 inches thick and a lower layer that is 2 inches
thick. For a three layer
mat, each layer would be 2 inches thick, while for a two layer mat, the core
would be 4
inches thick and the upper outer layer would be 2 inches thick. A crane or
timber mat would
be about 4 to 8 feet wide with beams having typical width and height
dimensions of 6x6,
8x8, 10x10 or 12x12 inches and a length of between about 20 and 40 feet. The
core
structure may be made of any environmentally resistant material disclosed
herein and in the
desired shape and configuration. The number of top, bottom, and core structure
components
will be dictated by the final dimensions of the mat for the particular
application or end use.
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Also, the preferred embodiments will include spacing in between top, middle,
and bottom
boards with is no wider than about 11/2 inches.
The core structure can be made up of different environmentally resistant
materials.
For example, a core structure of a sheet or plate of a thermoplastic or
thermosetting material
can be provided with a thin sheet of metal for additional reinforcement or for
maintaining
filler material in the cells or openings of the sheet or plate. A steel sheet
can be used upon a
layer of a thermoplastic material in the form of a sheet or other structure to
provide
stiffening of the core structure.
The core structure made of environmentally resistant materials prevents
degradation
from exposure to weather conditions in the event that water or other liquids
enter into the
core. Preferred specific environmentally resistant materials for the core
structure include:
various thermosetting materials, including Epoxy, Melamine formaldehyde
(MF), Phenol-formaldehyde (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.);
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;
a metal structure or frame of aluminum or stainless steel or of steel that is
coated, painted or galvanized to assist in preventing rusting when
contacting water; or
a reinforced plastic composite material as disclosed in US patent 4,629,358.
The edges of the core structure can be protected as disclosed in US patent
application
2014/0193196 or with wood or synthetic laminate to avoid mechanical damage to
core
structure edges. Additionally, a bumper structure of wood or plastic material
as disclosed
herein can also be used.
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For certain open cell core structures, reinforcement with sheets or other cell
closing
materials can be used to improve stiffness and strength of the core structure
while also
retaining the filler in the cells or openings.
It is also possible to use a metal plate as the core. The metal plate can
include
openings or apertures to reduce weight. A plate of a thermosetting plastic can
instead be
used, and it can be solid or have openings therein. The plates can be 2 to 4
inches thick. A
fiberglass reinforced thermosetting plastic grating having openings that are
2x2 or 3x3
inches is preferred.
To reduce the weight of the mat, the core structure can be made of a honeycomb
or
lath structure, or with a plurality of openings. For very open structures, the
cells or openings
can be filled as noted above with a material that is lighter than the metal to
maintain the
weight at a desired level. The openings can be covered with upper and/or lower
sheeting to
retain the filler therein. Any material can be used for the sheeting as the
metal core structure
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 preferably by riveting, bolting or by an
adhesive. The
sheeting and core structure can be maintained in position be being sandwiched
between the
outer layers, with the entire structure held together by bolting or riveting.
If necessary, holes
for the bolts or other fasteners can be drilled through the metal plate or
sheeting to facilitate
assembly by allowing passage of the fasteners therethrough.
Generally, the mat construction for a laminated mat comprises one of the cores
disclosed herein along with upper and lower layers of elongated members or
beams. For the
upper and lower layers, the thickness of the beams will be approximately 1.75
inches but
may be between 1.5 and 3 inches. Length will be as desired but will preferably
be 12, 14 or
16 feet. The width of the beams will vary depending upon location on the core.
That is, the
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. A typical thickness for the mat is at least about 4
inches and
preferably approximately 6 inches, with the central layer providing a
thickness of about 1 to
4 inches and the upper and lower layers providing a thickness of about 1 to 3
inches. Of
course, the dimensions can vary depending upon the specific end use intended
for the mat.
Also, the beams can be manufactured to any particular thickness, width and
length, but the
preferred dimensions disclosed herein approximate those of conventional mats
of white oak
or other materials which are in use in the industry.
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In a most preferred embodiment, the mat includes a core structure of an
environmentally resistant material, an outer upper layer positioned above the
core structure
and an outer lower layer positioned below the core, wherein each outer layer
includes a
plurality of elongated members each having a modulus of 1.6 M psi. As noted,
the core
structure is made of materials that provide a load bearing capacity that is
able to withstand a
load of at least 600 to 800 psi or more without damaging or permanently
deforming the core
structure.
The core structure can include one or two outer layers as desired or necessary
for a
particular installation and stiffness. The core structure components can be
made be of
sections or smaller portions that are joined together to form the desired size
of the core. As
an example, for a thermoplastic core structure of HDPE, sections may be welded
together to
provide the desired size, e.g., four HDPE 4 x 8 foot sections can form the
core structure of a
mat that is 8 x 16 feet. Similarly, eight 4 x 4 foot sections can be joined by
welding to form
the same 8 x 16 foot mat. The same is true of wood, metal or elastomeric
components,
which can be joined mechanically, by adhesives or where applicable by welding.
The core
structure can also be made of upper and lower half sections that can be joined
together by
welding, a mechanical interlocking, by fasteners or by adhesives.
Additional layers or components can be added to the core structure or mat, but
the
most preferred construction includes outer layers above and below the core
structure as
noted herein. The outer layers are preferably made of white oak as disclosed
in US patents
4,462,712 (three layer) and 5,822,944 (two layer), the entire content of each
of which is
expressly incorporated herein by reference thereto. The mats are generally
designed with
water channels on the outer layer(s) to drain water from the mat. This is
achieved by the
spacing of the elongated members or by the provision of grooves in a sheet or
other wider
surface that is presented on the outermost layers of the mat. The grooves are
generally
rectangular in shape and typically have a width of about 1.25 inch and a depth
of about 1
inch. It is of course also suitable to use channels that are U-shaped instead
of being
rectangular and that have a similar size as this achieves the same purpose of
providing a path
for moisture to be removed from the mat.
And while symmetrically formed mats are preferred, it is also possible to
provide a
core structure that has a different number of layers or plies on one surface
than another. For
example, the top surface of the core than include two layers or plies of
components such as
elongated or sheet members, while the lower surface can include only a single
layer or ply of
such components. And the materials used for the components of one outer layer
does not
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have to be the same as the materials used for other outer layers. Thus, the
mat designer has
abroad range of possibilities for mat construction to tailor a specific mat
for a particular
installation or need.
Referring now to the Figures, Figure 1 illustrates mat 100 that includes an
upper
outer layer 105 and lower outer layer 110 which are used to surround core
structure 115.
The core structure includes a plurality of reinforced polyester beams 125 and
the outer layers
include single width wood boards 130. The reinforced polyester beams 125 are
oriented
perpendicular to the boards of the upper and lower outer layers. As shown in
Figure 2, the
reinforced polyester beam 125 is in the form of a rectangular tube that has
two internal wall
supports 120 running along the interior of the tube.
Boards 125 are applied to the core structure 115 by nailing, screwing, bolting
or
riveting of the boards 125 to the reinforced polyester beams 125 of the core
structure 115.
When bolting is used, the bolts can extend from the upper boards to the lower
boards
through the reinforced polyester beams 125. The nails, screws or bolt heads
and nuts are
recessed below the top surface of boards 130 and below the bottom surface of
boards 130 to
present relatively smooth upper and lower surfaces of the mat 100.
Alternatively, the boards can be attached to the core structure 115 by an
adhesive or
other means that provide a secure attachment. For example, when the core
structure is made
of a thermosetting material, the sheet and boards can be made of the same
material as a
unitary component. For a metal core, holes can be drilled to allow the bolts
to pass
therethrough.
As shown in Figures 1 and 3, eleven (11) boards are used. The third, sixth,
and
ninth boards (135, 140, 145 respectively) of the lower outer layer are offset
to provide an
interlocking feature for the mat. And while offsetting of certain boards is
preferred 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.
And while the interlocking is shown on opposite sides of the mat, the mats can
be
interlocked together in any direction using the top or bottom layers with
appropriate
configuring of the components of those layers.
Lifting elements 150 are provided on the third and ninth boards of the upper
outer
layer. 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
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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 outer layer 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 3 illustrates the final shape and configuration of the mat 100 after
assembly.
Figure 4 illustrates a second mat 200 according to the invention which
includes a
lower outer layer 130 and a core structure 215 that has a plurality of cells
260. As some of
the components are the same as in Figures 1-3, the same numerals used are used
to designate
the same components for the mat of Figure 4. The core structure 215 may be
made of a
thermoplastic or metal and the cells can be left open or filled as disclosed
herein. The core
structure can also be a fiberglass reinforced thermosetting material in the
form of a grating
having square or rectangular openings therein. The openings or cells of the
core structure
may be filled with a foam or other material that expands to fill the cells 260
and remains
adhered thereto. In this situation, no cover member is needed to retain the
filler material in
the core structure 215. For that situation, or for the situation where the
cells are filled with
particulate matter, upper and lower layers 130 as described above can be
applied to the core
structure 215 to assist in retaining the particulate material in the cells
260.
Figure 5 illustrates a third mat 300 according to the invention which includes
a lower
outer layer 130, an upper outer layer 330 and a core structure 315 that has a
plurality of cells
360. As some of the components are the same as in Figures 1-4, the same
numerals used are
used to designate the same components for the mat of Figure 5. The core
structure 315 may
be made of a thermoplastic material or metal and the cells 360 are of
hexagonal shape to
provide larger openings can be left open or filled with particulate material
as disclosed
herein. In particular, the cells may be filled with foam, particulates or
other non-adherent
materials, e.g., rubber crumbles from recycled automobile tires. For such
particulates, the
cells 360 can be covered by one or more sheet members either above, below or
both above
and below the core structure to retain the non-adhering filler materials in
the cells. The sheet
members can be made of wood boards, plywood, plastic sheeting, metal sheeting,
e.g., steel
or aluminum, or the like. When the sheet members are only provided to hold the
filler
materials in the cells, they can be relatively thin e.g., 1/8 to1/2 inch is
sufficient although
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larger thicknesses can be used if desired to add weight to the mat. The core
structure and
sheet members can then be used as a core structure with outer layers applied
as in the other
embodiments.
Alternatively, when sheet members are not needed, the lower layer 130 and
upper
layer 330 can be wood boards that retain the filler in the cells 360 as shown
in Figure 5. In
this embodiment, when the core structure 315 is molded of plastic material,
the areas
between where the boards are placed would be made of solid plastic rather than
open cells so
that the particulate material does not exit the cells through the spacing
between the boards.
These boards would have a thickness of 1.6 inch or greater depending upon the
needed
weight of the mat. The filler also contributes to the weight of the mat.
Of course, if the material of the core structure 315 and lower 130 and upper
330
layers provides sufficient weight, the cells do not need to be filled and the
additional sheet
members are not needed. Additional sheet members are also not needed if the
cells are filled
with an adherent filler material. The boards 130 of the upper and/or lower
outer layers can
be attached by bolting which passes through the cells. If desired, and
preferably, the upper
outer layer 330 is provided so that the final mat structure has an appearance
that is similar to
that of Figure 3.
Another embodiment of the invention is a variation on that of Figure 5. The
core
structure is made of a plastic material that has cells made with flat upper
and lower surfaces.
These surfaces support the sheet members if the cells are filled and instead
support the lower
and upper layers if the cells are not filled. These cells thus act as shock
absorbers to provide
resilient compression to the mat.
In a preferred embodiment of the invention, the mat includes bumpers which
protect
the sides of the mat from damage during transport and installation. These
bumpers are
generally configured as a rails, rods or beams of a material that protects the
sides and core
structure of the mat from damage when being moved around from warehouse to
truck to
jobsite. As the mats are relatively heavy, around 2000 pounds, they are moved
by heavy
equipment such as front end loaders or cranes, and are typically dragged or
dropped into
position. The bumpers also provide protection to the side edges of the mats
due to such
movements and manipulation as well as some resistance to penetration by teeth
or tines of
the moving equipment. In one embodiment, the bumpers are made of a durable,
tough and
resilient material such as a plastic or elastomer, in particular, HDPE or a
rubber material
having a Shore D hardness of 10 to 50 is preferred. The bumpers are preferably
molded or
extruded into the desired shape or shapes for releasable attachment to the
mat.
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Figure 6 shows mat 400 which is configured as a Crane/Pipeline mat, typically
having dimensions of 8 inches thick by 4 feet wide and 18 feet long. These are
used
primarily for drilling rigs and similar applications such that these mats are
much more robust
and tough compared to mats for temporary roadways. To provide sufficient
strength, the
mat preferable includes a steel ladder frame 405 that provides the periphery
of the mat. The
frame 405 includes a number of cross-members to provide rigidity and strength
to the frame
to support the other mat components. The openings are provided to allow
connections to be
made and to reduce the overall weight of the mat compared to one made of solid
steel. A
core structure 410 is present within the ladder frame 405 and upper and lower
wood skins
415, 420 are provided to protect the core structure 405. The core structure
410 of the mat is
a solid or foam core structure preferably molded from HDPE or a similar
polymer. The use
of a polymeric core structure and the geometry/shape of the cells helps reduce
the overall
weight of the mat while providing sufficient internal support so that the mat
can provide the
necessary strength against compression and compaction. The wood skins 415, 420
provide
sufficient durability to equipment or vehicles that move over or that are
supported by the
mat. Also, the mat has openings that allow water or other liquids to pass
through during use.
As the core structure is made of environmentally resistant materials, there is
no need to
provide a hermetic seal about the core structure components of the mat.
As shown in Figure 6, the bumpers 425 are configured as an extruded or molded
rail
or rod that protects the sides of the mat. Generally, a single bumper
structure is provided
that is received in the open area of the I-beam that forms the periphery of
the mat. The
bumpers have a shape that fits within the open cavity of the I-beam without
completely
filling the area, as this allows the bumper to be compressed to absorb shock.
If desired, the
bumpers can be bolted, riveted or joined to the I-beam by an adhesive so that
they are
retained in position.
As shown, the bumpers in the enlarged view of mat 400 have a tri-tube
arrangement
430, of a "+" shape, that has a larger tube 430A in the center and the smaller
tubes 430B,
430C located above and below the central tube. The tubes can be extruded in
the shape that
is shown or separate tubes can be made and then j oined by welding, adhesive
bonding or
even by mechanical fasteners. This shape is not critical, however, and other
shapes that are
round, polygonal or that have combinations of different shapes can be used for
the bumpers
if desired. For certain materials, the bumper can fill the entire open side
cavity of the I-
beam, or it can partially fill the cavity provided that the bumper contacts
the inner wall of the
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I-beam and extends towards the periphery of the mat so that it can absorb
shock or impact
forces.
In other embodiments disclosed herein, the bumpers can be made of wood. Wood
is
a useful relatively low cost material that has a history of good service in
oil field mat
applications.
The bumpers are preferably located on all sides of the mat. To retain the
bumpers in
position in the I-beams, rather than using an adhesive of bolting, the upper
and lower layers
of the mat can be provided with an additional member that is nailed to the
upper and lower
wood skins to retain the bumpers in place to prevent their dislodgement from
the I-beam.
The bumpers provide protection to the sides of the mat as well as to avoid
damage to the
core structure components.
Figure 7 illustrates another Crane/Pipeline mat 500 that also includes a steel
ladder
frame 505 that provides the periphery of the mat. A similar foam core
structure 510 is
present within the ladder frame 505 and upper. Instead of upper and lower wood
skins,
however, the mat 500 of Figure 7 includes upper 515 and lower 520 vacuum
formed
polymer skins to protect the core structure 510. These skins can be formed to
a thickness of
up to 00.6" or greater. The skins preferably include lips 530 that engage the
upper and lower
portions of bumpers to retain them in place in the I-beams. Again, the bumpers
are shaped
as a plurality of joined tubes as shown in Figure 6 with upper and lower tubes
being of
smaller cross section than the center tube. The upper and lower tubes can also
be shaped to
engage in full contact the I-beam inner surfaces while being recessed from the
end of the
central tube so that the lips 530 can maintain the bumpers in place. Other
shapes for the
bumpers are acceptable provided that they can fit in the I-beam and provide an
outer surface
that can absorb shock and impact. For the configurations shown the tubes can
collapse
somewhat to absorb such forces.
The lip portions of the upper 515 and lower 520 skins can be a separate
component
that is attached to those layers or it can be molded or formed as an integral
part of those
layers. Generally, the upper 515 and lower 520 skins are made of a molded
plastic or
elastomeric material because such materials provide environmental resistance
and impart
durability and toughness to the mat. Also, the core structure 510 can be
provided in two
halves, an upper half that is attached to the upper skin and a lower half that
is attached to the
lower skin. These halves can be designed with protrusions or raised and lower
areas so that
they can be joined together by engagement of the protrusions and recesses or
raised and
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lower areas. This reduces installation time and also assures that the core
structure and skins
interlock to provide the best resistance against compressive forces.
In the embodiments of Figure 6 and 7, the steel frame can be painted or coated
with a
sacrificial metal (i.e., galvanized or phosphatized) to provide improved
environmental
resistance to the mat. While rusting of the steel is not detrimental to the
operation of the
mat, it does not provide a good cosmetic appearance such that the painting and
coating
compensate for that by minimizing rusting. Stainless steel can also be used
but that material
is more expensive. Aluminum can also be used but some strength to the mat is
lost with that
lighter weight construction. The metal ladder frame is advantageous because,
in addition to
its strength and ease of working, it can be configured to allow direct
attachment of the lifting
elements to the frame 505 to provide a more robust connection that facilitates
lifting and
manipulation of the mat.
As in Figure 6, the mat of Figure 7 has a reduced overall weight by
incorporating the
molded or structural foam core structure in the steel frame. Whether the upper
and lower
layers are made of wood or of a plastic or elastomeric material, the entire
structure is bolted
or riveted together to form the final mat.
To further reduce the weight of the mat while also improving its environmental
resistance, a box frame of fiberglass reinforced plastic (FRP) can be used
instead of the steel
frame. This is shown in Figure 8, in mat 600, that has a FRP box frame 605.
The box frame
605 may be made of rectangular or square tubular structures. If desired, the
FRP box frame
605 can be configured as a ladder frame as shown in Figures 6 and 7. The FRP
frame
provides lower weight and good durability and resistance to moisture of other
liquids that
may permeate into the core. To provide additional crush resistance to the
frame 605, the
open center portions of the tubes can be filled with foam, recycled rubber
tire material or
other filler material 610. A polyurethane foam can also be used for this
purpose. The filler
material can also be selected to provide additional weight to the mat if
desired.
The plastic of the FRP material would be any one of the thermosetting plastics
of the
types mentioned herein but thermosetting polyesters and epoxies are preferred.
Figure 8 illustrates another feature of the invention where the molded foam
core
structure 612 is locked in place by engaging pockets 617 in the upper 615 and
lower 620
polymer skins.
When a box frame is used, the bumpers 625 are configured with a flat surface
to abut
against the frame 605. The bumpers 625 are configured with upper and lower
portions that
are less wide than the central portion of the bumpers so that the skins 615,
620 can include
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lips 630 that engage the bumpers 625 to hold them in place against the box
frame 605.
These lips are essentially the same as those shown in Figure 7. The bumpers
protect the FRP
box frame from damage since the FRP box frame is not as strong as the steel
ladder of
Figures 6 and 7. The FRP beams may be made by a pultruded process as this
results in a
light but strong construction.
In Figure 8, the upper 615 and lower 620 polymer skins can be configured with
protrusions or honeycombs that interlock with the core structure 612 to form a
more rigid
structure. Alternatively, the foam core structure 612 can be omitted and the
open center of
the mat filled recycled rubber tire material or other particulate filler
material as is done with
the central opening of the pultruded FRP box frame.
Alternatively, rather than fit into the structure on the sides of the mat, the
bumpers
can be designed with a "C" shaped cross section so that they can contact the
top, side and
bottom of the pultruded FRP box frame members. The top and bottom surfaces of
the
bumpers can extend above the upper and lower surfaces of the mat or they can
be designed
to remain flush with those surfaces by providing a thickness on the top and
bottom bumper
portions that correspond to the thickness of the top and bottom layers.
Alternatively, the
bumpers can be bolted, screwed, snap riveted or adhered to the FRP box frame
with an
adhesive.
Figure 9 illustrates the same type of mat as in Figure 8 such that the same
numbers
are used to describe it. The main difference in the mat 700 of Figure 9 is
that the box fame
605 is not filled and is open 710 as for certain embodiments, the filler is
not necessary. The
bumpers in Figures 8 and 9 have a "T" shape with the central portion
protruding beyond the
sides of the mat to provide protection of the FPR frame and core.
Figure 10 illustrates another embodiment of a Crane/Pipeline mat 800 that
includes a
box frame 805 of an FRP square tube. The box frame 805 surrounds a laminated
wood core
810. Although the wood core 810 is heavier than the foam core of the other
embodiments, it
is much less expensive and can be used in certain installations where the
greater weight or
ruggedness of the mat is needed. The oak core boards are configured to fit
within the
openings of the box frame 805 and are bolted together so that they do not move
around
inside of the mat. Oak boards are also used as the top 815 and bottom 820
surfaces of the
mat 800.
The FRP frame 805 is protected by a rectangular wooden structure 825 which is
also
made of oak boards. The boards are joined together to form a square structure
that is
approximately the same size as the box frame 805 in width and height
dimensions although
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the perimeter is larger so that the structure 825 sits outside or and adjacent
to the box frame
805. The wood structure 825 acts as a bumper to protect the FRP box frame from
damage
during loading, transport and installation.
To provide additional protection to the box frame 805, the open area of the
frame can
be provided with a stabilizer 830 of foam or extruded polymer. As in Figure 8,
the open area
can be can be filled with recycled rubber tire material or other particulate
or solid filler
material. One variation of the stabilizer 830 is shown in Figure 10 but the
bumpers and solid
foam inserts of the other embodiments can be used as well, depending upon the
desires of
the designer of the mat. The wood structure most likely obviates the need for
stabilizers for
most installations.
Figure 11 illustrates another embodiment of a mat 900 that includes a frame
905
constructed of a metal such as aluminum, stainless steel or steel. The frame
905 is made of
square or rectangular tubing that is welded together to provide a high
strength core
component for the mat. The frame 905 can remain as an open structure as shown
or areas
910 between the cross members can be provided with a particulate filler or
foam that is
retained in place by a mesh, screen or sheets that are secured to the top and
bottom of the
frame. Also, if desired, the tubes can be filled with a foam, rubber particles
or even sand to
add weight and strength to the mat. If desired, a wood core can be used along
with or
instead of the fillers. Preferably, however, the areas are left free of any
filler.
The mat 900 includes top 920 and bottom 925 wood boards preferably of oak that
provide a flat surface for movement of vehicles or supporting equipment
thereupon. These
boards also provide upper and lower surfaces of the mat and protection of the
core structure
905. These boards 920,925 also have spacings between them to allow water to
drain from
the upper surface of the mat, into the core structure and out of the lower
surface of the mat.
As the core structure 905 is made of an environmentally resistant material,
there is no
concern of deteriorating the core structure due to contact with water. The top
and bottom
wood boards are joined together about the frame using nails or bolts. Also,
the tubular
members of the frame 905 can also be provided with holes passing therethrough
to
accommodate bolting that is used to attach the wood boards 920,925 to the
frame 905.
The frame 905 is also protected by wood boards 915 that provide replaceable
bumpers for the frame 905. These can be attached to the frame by bolting that
engages holes
in the tubular members, or the wood boards 915 can be attached to the upper or
lower boards
920, 925. As an alternative connection member, the frame 905 can be provided
with studs or
bolts that are welded to the tubular members and that receive the bumpers 915
or the upper
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920 or lower 925 boards by passing through correspondingly located holes in
those boards.
The boards are then secured to the frame by appropriate nuts and washers or by
flattening of
the studs. This provides a simple yet robust construction for mat 900 which as
noted allows
replacement of boards that may become damaged during use. In the embodiments
of Figures
9 to 11, the top boards can be 1.25" by 16" wide although smaller sections can
be joined
together if desired. The box frame has a preferred size of about 5.5 by 5.5
inches so that the
mat has an overall thickness of about 6 inches.
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
material of uniform flatness (i.e., within +/- 12 inches over an 8 x 14 foot
surface). Crushed
stone or rock no larger than 4 inches 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 feet wide x 6 inches
thick and
are either 12, 14 or 16 feet 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.
The mats typically include two (2) outer layers of individual wood or
composite
boards, having cross section dimensions of 1.75 by 8 inches.
The spacing between individual boards or components in the upper outer layer
is
preferably approximately 1.25 inch to allow water to drain from the mat. This
spacing is
retained in the upper portion of the skin. The slip resistance of the mat is
improved by the
draining of the excess water, especially when used in locations that
experience heavy rain or
snow conditions. The spacing between the individual boards or components can
also be
provided on the lower outer layer of the mat to allow the mat to provide
better gripping onto
the ground. The spacing or similar grooves on the lower outer layer on the
bottom of mat
will keep the mat from moving around on the ground as traffic moves across it.
The spacing
or grooves re even more important when the lower portion of the mat is made of
an
elastomeric or thermoplastic material so that the mat would it grip the ground
sufficiently
and will avoid or reduce sliding or slipping thereon.
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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 structure of the mat. The core structure 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 resistance to torsion
forces that
applied to the mat by vehicles passing thereover. Generally, the cores are
designed so that
they provide some degree of compressibility as large vehicles or equipment
move over or are
placed upon the mat. After the vehicles or equipment are removed from the mat,
it retains its
original thickness. In wet environments, this can cause some water to be
sucked into the
mat, which is another reason why the core structure components are designed to
withstand
moisture. Also, for some embodiments, the mats may be designed with apertures
so that any
water that enters the mat can later exit.
And while the preferred crane or timber mat sizes are about 6x6, 8x8 or 12x12
inches
by 8 feet wide and 20 to 40 feet long, a related type of mat that is used with
these large mats
are the ramp mats or transition mats. These both have the same type of
construction as the
crane mats but are cut down in size to 3x3 inch or 4x4 inch in various lengths
of 10 or 20
feet or more. These ramp or transition mats are positioned along one or more
of the sides or
ends of crane mats to act effectively as a "step" that allows heavy equipment
to more easily
move onto the larger crane mat.
Optionally and preferably, the perimeter edges of the mat are provided with
additional protection to prevent or reduce damage to the core structure
construction of the
mat from side entrance or egress onto the mat from large vehicles with steel
tracks. The
edge material helps protect the core structure and bumpers and is preferably
easily
removable so that it can be replaced when necessary.
When plastic materials are used for the core, they are formulated to be
relatively
inflammable. Flammability of mat shall be defined as Class 2 (B) flame spread
when
measured by ASTM E84 test criteria. The flammability properties of these
materials can be
enhanced by adding the appropriate conventional flame retardant or other
additives that are
known to impart such properties.
The core structure can also be formulated to allow dissipation of static
electricity.
For this purpose, carbon black, metal particles or other conductive fillers
can be added to
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plastic materials that are used for the core. Of course, a metal core
structure is conductive
without any additives.
Although relatively protected by the outer layers, the core, when made of
plastic
materials, can contain UV inhibitors as necessary and in an amount sufficient
to reduce
deterioration of physical properties or color.
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-shaped
rings, 0-shaped rings, chain, or cables at 2-4 locations on the upper surface
of the outer layer
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 mat during
transport and
installation.
The core structure of the mat may or may not be hollow. If hollow components
are
used for the core, whether as tubes of cells that have openings, these
openings are preferably
filled with a non-absorbent filler material. A wide variety of different
plastic, elastomeric or
foam materials in particulate or other forms can be used for this purpose. The
hollow
portions can be used as is or can be provided with the filler material 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 friendly materials can instead be used.
Preferably, the mat
has a weight that is on the order of an oak mat of similar size.
When elongated members are used for the upper and lower layers of the core
structure construction, they provide additional weight to the mat and can be
configured in
different ways. One way would be to replicate a conventional oak mat and
provide a single
width construction where eleven 6 inch wide (by 12, 14 or 16 feet 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. Alternatively, a double width construction may be used where
four 12 inch
wide (by 12 or 16 feet long) boards are provided in the upper and lower
layers: each one
separated by a 6 inch board with the three 6 inch boards in the lower layer
offset to provide
interlocking. Other configurations can be used as desired for the particular
end use of the
mat.
If desired, the boards can made of wood or engineered lumber (preferably with
a
tolerance of 1/16 inch) or they can be made of tubes of metal or of a
thermoplastic,
elastomeric, or thermosetting material, with pultruded thermosetting tube
being one example
of a preferred alternative material. The sizes mentioned herein are not
critical and can be
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varied depending upon the intended use of the mats. The values mentioned above
are
representative of typical mats.
The upper, central and lower layers are typically nailed and/or bolted
together to
form the mat. The structure preferably has a modulus of about 1.6 M psi
although plastic
mats may have a lesser modulus when greater flexibility of the mat is desired.
The mat
compression property of 600 to 800 psi is suitable for most applications.
Figures 12 and 13 illustrate a first embodiment of the invention in the form
of a mat
1100 having substantially flat top and bottom surfaces. Although the bottom
surface of the
mat is not shown in these figures, the mat is preferably made with the same
structure on both
surfaces so that either one can be used as the upper surface of the mat that
is to receive
equipment or vehicles thereon. While this facilitates installation in that
there is no
requirement for placement of the mat in a particular orientation, it also
allows the installer to
select the surface of the mat that is in better condition to be used as the
upper surface of the
mat.
The mat 1100 includes first and second side beams (1105, 1110) having top,
side and
bottom surfaces, with the beams having width and height dimensions of between
6x6 inches
and 24x24 inches and a length of at least 4 feet and typically between 10 and
60 feet.
Preferably the lengths of the beams are in the range of 20 to 40 feet and
preferably 30 to 40
feet as these length mats are easier to transport and ship compared to longer
mats. Other
dimensions that are typically used for the side beams are 8x8, 10x10, 12x12,
14x14 and
16x16 although a skilled artisan can select other dimensions as desired.
Typically, the widths and heights of the side beams are of the same dimension
so that
the beams have a square cross-section. Alternatively, for certain designs, the
beams may be
rectangular in cross section, with the width being about twice the dimension
of the height or
vice versa. Other typical dimensions are 6x12, 6x18, 8x10, 8x12, 12x14, 12x16,
12x24, and
18x24. These rectangular beams may be connected to the support structure with
the longer
side as the height or with the longer side as the width, depending upon the
desired use of the
mat. Using the longer side as the width is generally preferred for
interlocking mat
arrangements.
A support structure 1115 is located between and connecting the first and
second side
beams (1105, 1110), with the support structure having upper, lower and side
portions, a
height that is less than that of the side beams, a width and a length. The
support structure,
which is set forth in more detail in Figure 14, includes first and second
longitudinal members
(1120, 1125) that are joined together by a plurality of cross members 1130.
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The support structure 1115 may be made of steel components with the cross
members 1130 welded to the longitudinal members 1120, 1125 to form a ladder
type
structure which forms a frame for the support structure. At the front and rear
ends of the
frame, additional cross members 1135, 1140 may be provided to form a
peripheral
rectangular structure. For this embodiment, it is preferred that both the
longitudinal
members and additional cross members 1135, 1140 be C-shaped beams having a
relatively
flat plate with upper and lower flanges directed away from one side of the
plate. The surface
of the flat plate opposite the flanges of the longitudinal members faces the
side beams 1105,
1110 so that a close and secure connection can be made between the two. The
flanges of the
C-shaped beam also serve as a point of connection for elongated members (1145
A, 1145B:
1150A, 1150B). Bolts 1155 can be attached to the flanges or to the cross
members for this
purpose. The flanges of cross-members 1135, 1140 also face the interior of the
support
structure so that the ends of the ladder frame have relatively smooth faces.
The cross members 1130 can be attached to the C-shaped beam between the top
and
bottom flanges to form vertical connectors of the support structure that
provide the desired
strength and rigidity. As shown in Figures 13 and 14, the resulting structure
is a rectangular
box frame with spaced cross members on the front, back, top and bottom.
The cross members 1130 of the support structure greatly contribute to the
stiffness
and rigidity of the frame. These members are typically spaced 12 to 24 inches
apart for
support structures that are used for the smaller sizes of height and width
beams. For larger
size beams, the spacing can be reduced to 10 to 16 inches in order to provide
sufficient
strength to hold the mat together. The determination of the spacing of the
cross members
can be calculated for any particular size mat using generally known
engineering guidelines
and equations so a more detailed explanation is not needed herein. The cross
members
typically have a height that is at least half the height of the longitudinal
members to which
they are attached and preferably are about the same height as the longitudinal
members. If
desired, reinforcement members can be added to the structure. In one such
arrangement,
additional plates, rods, beams or other structural components can be added to
the top and/or
bottom portions of the support structure between the longitudinal members.
This is certainly
advantageous when supporting the largest or heaviest equipment on the mat.
Also, other
structural members can be provided between the cross members however in most
situations
this is not necessary. If additional reinforcement is needed, care must be
taken for
positioning such members to avoid blocking or interfering with the passage of
the joining
rods through the longitudinal members and into the support structure.
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The C-shaped beam and cross members are typically made of a metal such as
steel so
that the structure can be made by welding the cross members to the beams.
While the
preferred construction of the metal frame of the support structure is by
welding, the frame
components can instead be joined together by brazing, rivets or bolting if
desired depending
upon the size and configuration of the overall support structure. Instead of a
C-shaped beam,
a flat plate (i.e., one without flanges) of the appropriate thickness can be
used. For this
arrangement, the cross members may have an I-beam shape to provide further
strengthening
of the support structure. A C-shaped steel beam is preferred for the
longitudinal members,
however, because the flanges provide additional rigidity and support to the
structure as well
as support for the cross members during installation. Of course, this can be
compensated for
by using a thicker flat plate for the longitudinal members when that
embodiment is to be
used. And the I-shaped beams can be used for the cross member when a C-shaped
longitudinal member is used, with appropriate adjustments made where the
flanges of each
come into contact with each other.
When the components of the support structures are made of metal, steel is
typically
used as that material is readily available and of low-cost. Although not
necessary for most
applications, the support structure can instead be made of a more corrosion
resistant material
such as stainless steel, copper, bronze, or other alloys. When carbon steel is
used, however,
the corrosion resistance can be enhanced by painting or coating the structure
so that it would
be more resistant to moisture. Also, steel can be galvanized or provided with
another type of
protective coating so that it would have a lower tendency to rust when
contacted by
moisture.
Aluminum or titanium can also be used for the support structure in specialty
applications. All of these materials generally have higher cost than steel and
can present
joining the problems of greater difficulties in welding or brazing the cross
members to the
longitudinal members. It is possible in an alternative embodiment as noted to
use rivets or
bolting to connect the various longitudinal and cross members together to form
the frame of
the support structure. The sizing of the rivets or bolts as well as the
dimensions for the
welding and brazing, can be readily determined by a skilled artisans using
routine testing if
necessary. The same is true for the thickness of the beams or members that are
used in the
frame structure.
Alternatively, the support structure may be made of a fiberglass reinforced
thermosetting plastic material resin, which is typically a polyester or epoxy
resin. The
components of the structure may be pultruded in the form of a rectangular or
square tube
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which may be hollow or filled with other materials depending on the overall
weight and
compressibility desired for the construction.
When fiberglass reinforced thermosetting plastic material is used to form the
support
structure, the box or ladder frame can be prepared in the desired shape with
the cross
members and longitudinal members joined together with resin prior to curing.
It is also
possible to utilize bolting or other mechanical fasteners to connect these
components
together.
A plurality of joining rods 1160 are used to attach the side beams to the
support
structure, with the joining rods passing through the sides of the beams and
support structure.
These joining rods 1160 are typically large carriage bolts that include
threaded ends to
receive nuts that when assembled will hold the components together. These rods
are spaced
about 3 to 6 feet apart depending upon the size of the mat. Figure 13 shows
the rods 1160
passing through side beam 1105 and toward the side structure: Figure 14 shows
how the rods
1160 would appear when present in the support structure. These carriage bolts
are typically
made of a high strength steel. Also, in some embodiments, the beams can
include a sleeve
that facilitates passage of the bolts through the support core. The sleeve can
be a flanged
hollow tube that extends through the support core and if desired into one side
beam and part
of the opposite side beam. The tube would terminate in the opposite beam so
that it would
not interfere with the net that engages the threaded end of the bolt. The
sleeves are shown in
Figure 14 as elements 1165.
To form a substantially flat surface on the mat, various elongated members for
upper
and lower elongated members (1145A, 1145B, 1150A, 1150B) are provided. A first
plurality of elongated members (1145A, 1145B) are attached to an upper portion
of the
support structure 1115 while a second plurality of elongated members is
attached to a lower
portion of the support structure 1115. Thus, the top surface of the mat is
formed by the top
surfaces of the side beams 1105, 1110 and the first plurality of elongated
members 1145A,
1145B , while the bottom surface of the mat is formed by the bottom surfaces
of the side
beams 1105, 1110 and the second plurality of elongated members 1150A, 1150B.
The flat
top surface of the mat is best shown in Figure 12.
As the upper and lower surfaces of the mat must be somewhat uniform, the
support
structure and upper and lower elongated members generally have a combined
height that is
the same as that of the side beams. Typically, the support structure is
centered vertically
with respect to the side beams. As an example, the side beams can be 12x12 and
the support
structure would have a height of 8 inches so that the beams extend 2 inches
above the top of
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the support structure and 2 inches below the bottom of the support structure.
This provides
room on the top and bottom of the support structure to accommodate 2 inch
thick elongated
members so that the top and bottom of the mat has substantially uniform
surfaces. This type
construction is preferred in that it minimizes the different types of
thickness that need to be
used for the elongated members and also provides a symmetrical mat that be
oriented with
wither surface facing up to receive equipment thereon. In other embodiments,
different
thicknesses of elongated members can be used on the top than on the bottom
with the intent
being that the thinner members are used on the bottom to prevent dirt or other
materials from
entering the support structure, while the elongated members on the top surface
are provide to
support the equipment or vehicles that are located or move upon the mat. In
this
embodiment, it is possible to provide a flat plate on the support structure of
the lower surface
rather than elongated members.
The same is true for the ends of the support structures. The longitudinal
members
1120, 1125 can be shorter than the length of the side beams 1105,1110 by a
distance of about
1 to 24 inches on each end or by a total of 2 to 48 inches. The distance of
the shortened ends
can correspond to the width of the side beams, if desired. The space between
the shortened
ends of the support structure 1115 and the side beams can be filled in with
bumper members
1175, 1180 which then allow the mat to have substantially flat front had rear
ends. These
bumper members can be of the same width as the elongated members so that the
same
material for the elongated members can be used to provide bumper members for
the front
and rear of the support. This creates a symmetrical structure but different
thicknesses of the
bumper members can be used if desired.
In a less preferred embodiment, the longitudinal members 1120, 1125 can be
substantially the same length as that of the side beams 1105,1110 so that the
front and rear
cross members 1135, 1140 form with the ends of the side beams the front and
rear end
surfaces of the mat.
The mat must also provide sufficient load bearing capacity: A fully supported
mat
(one that is properly installed on a suitable prepared ground surface) must be
able to
withstand a 10 ton load, spread over a 12 inch diameter surface without
degradation of mat
properties or permanent deformation of the mat. The support structure would
have a crush
resistance of between about 500 and 800 psi to possibly as much as 1000 psi
depending upon
the application and when properly installed on a suitably prepared ground
surface. This
provides resistance against compression as large vehicles or equipment move
over or are
placed upon the mat.
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The side beams of the mat prevent or reduce damage to the support structure
from
side entrance or egress onto the mat from large vehicles with steel tracks.
These beams can
be replaced when necessary while the support structure can be reused to make a
new mat.
The elongated members as well as the side beams are preferably made of any
type of
wood although oak is typically preferred. These members may also be made of
engineered
wood or lumber since that will be easier to make long lengths without having
to obtain one
piece virgin wood lengths. Additionally a layered veneer laminate can also be
used for these
members or beams. It is expected that the cost for that material would be
about the same as
the price for oak thus making it an attractive alternative.
Engineered lumber (or engineered wood) includes a range of derivative wood
products which are manufactured by binding or fixing the strands, particles,
fibers, or
veneers or boards of wood, together with adhesives, or other methods of
fixation to form
wood composite materials.
These materials provide the surprising benefit of repeatable consistency of
the required sizes,
the ability to mix different wood species to arrive at the final product, and
exceptional
properties generally exceeding what is provided from monolithic boards.
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 inches, in widths from about 2 inches
to 54 inches, and in lengths of about 8 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.
Alternatively, the side beams and elongated members may be made of a
fiberglass
reinforced thermosetting plastic material such as fiberglass reinforced
polyester or epoxy
resins. These materials may be pultruded into a solid form or preferably as a
rectangular or
square tube. If desired, hollow tubes can be filled with any one of a variety
of materials to
contribute to the overall strength or compression resistance of the tube.
Typically, crumb
rubber, recycled tires or other plastic or elastomeric materials, sand,
crushed rock or
polyurethane foam may be provided inside the tube either before or after
attachment to the
support structure. A polyurethane foam is preferred for this purpose as it can
be injected in a
liquid form after the pultrusion is attached to the support structure. For
stronger or heavier
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filler, the joining rods may be initially placed into the beam so that the
filler does not block
the insertion of the rods when joining the side beams to the support
structure. Additionally,
a metal or pultruded plastic tubular sleeve can be provided in the beams at
the locations
where the rods are to be inserted, so that the rod has an opening that remains
after the filler is
placed into the beams.
As these mats are relatively massive, provision should be made for moving,
transporting and installing the mat at the desired field location. For this
purpose, holes are
provided in the upper surface, lower surface, or both to provide access to one
or more of the
joining rods. These holes are formed as cut out portions 1185 of the elongated
members
1145, 1150. In this way, the holes allow access by a hook from a crane or
other mechanical
attachment to the joining rods for lifting or manipulation of the mat. For
convenience, the
attachment openings 1185 are provided both on the upper and lower surfaces of
the mat so
that either surface can contact the ground or be exposed on top as the surface
upon which the
equipment is to be installed, thus facilitating installation.
Turning now to Figures 15 and 16, an alternative embodiment of the present
invention is illustrated, in the form of a mat having side beams configured
and dimensioned
to allow interlocking of adjacent mats. Where like components are used from
the previous
embodiment, the same reference numerals will be used in Figures 15 and 16 and
only the
different features of this alternative embodiment will be described.
Mat 1200 includes side beams 1205, 1210 which are configured and dimensioned
to
represent only one half of the thickness of the mat. On one side of the mat,
beam 1205 is
attached to the upper portion of the support core 1215. This is done in a
manner to extend
the upper surface of beam 1205 above the top surface of the support structure
1215. As in
the prior embodiment, elongated members 1145A, 1145B can be provided on the
top portion
of the support structure 1215 so that the top surface of the mat adjacent the
side beam 1205
is relatively flat. In a similar manner, side beam 1210, which also has a
thickness that is one
half the thickness of the entire mat, is mounted to a lower end of the support
structure 1215.
The lower surface of side beam 1210 extends below the lower surface of the
support
structure to allow elongated members 1150A, 1150B to be accommodated to form a
substantially flat surface for the bottom of the mat adjacent beam 1210.
This structure allows one mat to be initially placed on the ground with an
adjacent
mat placed such that beam 1205 sits upon beam 1210. This arrangement can be
continued
for as many mats as necessary to achieve a desired working base for cranes or
other
equipment.
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The top surface of mat 1200 has a step on the opposite side from beam 1205,
above
beam 1210, while there remains an open space or step below beam 1205 adjacent
the lower
surface of the matt opposite beam 1210. While these surfaces allow
interlocking of adjacent
mats, it does not provide a stable mat surface on the outermost sides of the
working base. To
compensate for this, modified mats can be provided wherein the outermost end
mats on one
side of the working base can be made with beam 1105, which is the full
thickness of the mat,
on one aside and with beam 1210 on the opposite side to allow interlocking
with adjacent
mats that are configured like mat 1200. Similarly, the outermost end mats on
the opposite
side of the working base can be made with beams 1110 instead of 1210 on one
side beam
1205 on the opposite side.
Alternatively, when the full extent of the entire working base is not known,
of if an
insufficient number of modified mats are not available, the mats on the
outermost sides of
the final working base can be provided with stabilizing beams of the same size
and
dimensions as beam 1205 provided in the space below attached beam 1205 so that
the side
of the mat can be stabilized. The same thing can be done for the outermost
mats that have a
step above beam 1210. A separate stabilizing member can be provided of the
same size as
beam 1210 to finish the upper surface of the mat at those locations. The
stabilizing members
can be attached to the beams of the mat if desired.
Mat 1200 requires a different system for connecting the beams 1205, 1210 to
the
support structure 1215. The connection of beam 1205 to the support structure
1215 will
require that the joining rods 1260A pass through an upper portion of the
support structure,
whereas beam 1210 is connected to the support structure with joining rods
1260B passing
through the beam and a lower portion of the support structure 1215. This is
best shown in
Figure 16 where the relative positions of the joining rods 1260A, 1260B are
illustrated,
along with sleeves 1265A, 1265B. A number of additional features may be
provided in the
mats of the present invention.
Figure 17 illustrates a further variation of the invention, wherein mat 1200
includes
an radio frequency identification (RFID) tag 1275 which is located in the
core.
Alternatively, this RFID tag 1275 can be embedded in an outer layer in an
opening or a
routered pocket to enable the mat 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
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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 outer
layers or core structure of the mat so that it is protected from damage during
use. 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. It also may be covered with a plexiglass film to prevent its removal
by abrasion.
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
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 outer layer. Figure 17 illustrates the locating
of LED lights
1285 in the core structure beneath elongated member 1245A. The lighting is
covered with a
clear material 1295 of plexiglass, so that the lighting element may be better
protected against
damage during use. To achieve the desired lighting brightness, the skilled
artisan can
provide the necessary number of lighting elements, or can include lighting
elements of larger
size.
Another feature of the invention is the use of color coding to identify the
specific
layers that are used in the construction of the mat. 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" that identifies the specific core
structure that is present in
the mat or a particular end user or owner of the mat.
Figures 18 and 19 illustrate a crane/pipeline mat 1300 that has a typical
thickness of
about 8 to 12 inches, a typical width of about 4 feet and a typical length of
between 12 and
20 feet. The mat 1300 includes two side beams 1305, 1310, a steel box frame
1320, an
upper layer of elongated members 1315A, 1315B, 1315C, and a lower layer of
elongated
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members 1325A, 1325B, 1325C. The core structure can be between 2 and 3 feet
wide
depending upon the width of the side beams.
The steel frame 1320 includes a forward lifting element 1335 and two upper
side
lifting elements 1340. If desired, a rear lifting element and two lower side
lifting elements
(not shown) can also be provided. These lifting elements allowed the mat to be
lifted
overhead by a crane having a suitable lifting capacity to facilitate loading,
unloading, and
installing of the mats. The lifting elements can be constructed as desired. If
cables or chains
are to be used, any holes made in the mat for such cables or chains must be
drilled through
the entire mat, and not just looped in between board or component spacings.
The chains or
cables must have at least three drop forged clamps. Cable must be new 3/4 inch
steel core,
extra improved plow (EIPS), right regular lay wire rope, having a minimum
breaking
strength of over 29 tons. Chains should be 3/8" high test chain, having a
working load limit
of 5400 lbs. and a minimum breaking strength of 16,200 lbs. with 3/8 inch
double clevis
links, in order to provide a safe working load limit of about 5400 lbs.
Other lifting elements may be used, such as those described in US patent
application
62/211,664 filed August 28, 2015, the entire content of which is expressly
incorporated
herein by reference thereto. Those lifting elements can be used with any of
the mats
disclosed herein provided that the appropriate core structure is present.
The components of mat 1300 are more clearly shown in the exploded drawing of
Figure 19. The steel frame 1320 is shown as having a plurality of components
including two
elongated side components, a front component, a back component and two cross
members
1345, all of which are welded or bolted together to form the frame 1320. Side
beam bolting
members 1335 are also welded to the box frame 1320. These bolting members are
configured to pass through openings in the side beams 1305, 1310 to secure the
side beams
to the steel box frame 1320. This is done by tightening nuts onto the ends of
the bolting
members 1335 after they pass through the holes in the side beams. The side
beam holes are
recessed so that the bolting and nuts do not extend beyond the sides of the
beams.
The lifting elements 1330, 1340 are preferably in the shape of a D ring which
is
welded or bolted to the box frame 1320 or its cross members 1345 as best shown
in Figure
19. The upper layer elongated members 1315A, 1315B, 1315C, and lower layer
elongated
members 1325A, 1325B, 1325C are also bolted to the box frame 1320.
As the box frame 1320 defines open areas therein, it is best to fill those
open areas
with material that will contribute to the ruggedness and weight of the mat. In
particular, a
filler of wood members 1350 that either are scrap pieces from the production
of other mats
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or are end grain or engineered wood can be used. It is also possible to use a
less expensive
wood material such as treated pine because the purpose of these filler
materials is simply to
add weight to the mat and they are not exposed to wear or abuse. And instead
of wood
material, the open areas of the core may be filled with other materials
disclosed herein.
Figures 20 and 21 illustrate yet another mat 1400 that includes a steel frame
core
1410. The core is used on an interlocking mat that has upper 1405 and lower
1415 layers of
elongated members. These elongated members may be made of wood, engineered
wood, or
of a thermoplastic, elastomeric, rubber, or thermosetting plastic material.
The plastic and
elastomeric or rubber materials can be used alone or can be reinforced as
known in the art to
provide additional strength, abrasion or wear resistance or to otherwise
improve physical
properties. Preferably, wood is preferred as it provides abrasion and abuse
protection to the
mat at a relatively low cost. And as shown, three elongated members 1415A,
1415B, 1415C
of the lower layer are offset from the others to form a configuration for
interlocking with an
adjacent similarly configured mat as disclosed elsewhere herein.
The steel frame 1410 includes four side members and two cross members 1420
which can be welded or bolted together to form the frame. The open space in
the box frame
can be filled with material that will contribute to the ruggedness and weight
of the mat. In
particular, a filler of wood members 1450 that either are scrap pieces from
the production of
other mats or are end grain or engineered wood can be used. It is also
possible to use a less
expensive wood material such as treated pine because the purpose of these
filler materials is
simply to add weight to the mat and they are not exposed to wear or abuse. And
instead of
wood material, the open areas of the core may be filled with other materials
of the types
disclosed elsewhere herein.
To protect a steel frame from damage, a rectangular bumper configuration 1440
is
provided along all outer side surfaces of the steel box frame.
And as in the other embodiments, D-shaped lifting elements can be 1445 can be
provided in various locations on the top and bottom of the mat in positions
where they can
be welded to the cross members 1420 of the steel frame. These would allow
lifting of the
mat and transport as well as placement into the appropriate locations during
installation.
Figure 22 illustrates a preferred embodiment of the invention wherein the
environmentally resistant core of the mat 1500 is a fiberglass reinforced
polyester or epoxy
grating 1505 having a thickness of 3 inches and with grating openings of 2x2
inches. The
same upper 1510 and lower 1515 wood structures of Figures 20-21 can also be
used for this
mat, with all of the components bolted together. As noted herein, the grating
can have a
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greater or lesser thickness ranging from about 2.5 to 4 inches in thickness
with openings of
between 1.5x1.5 inches and 3x3 inches. The grating can be made to essentially
the same
length and width of the overall mat, i.e., exactly the same dimensions or an
inch or two
shorter on each dimension so that the grating is protected by the wider wood
portions of the
mat. And instead of being made as a single piece, it may be preferable in
certain situations
to make a number of smaller gratings so that 2, 3, 4 or 6 of them are placed
adjacent each
other to represent the overall length and width of the mat. This is shown in
Figure as 4
smaller gratings that when placed adjacent each other are the same overall
size as the upper
and lower layers of the mat. The smaller sections can be placed horizontally
across the
width of the mat or they can be in different widths that when combined span
the width of the
mat.
Of course, it is also possible to utilize a solid fiberglass reinforced
thermosetting
resin sheet of the thicknesses mentioned herein either by itself or with
apertures or openings
cut therein. As shown, the bolting would pass through the entire construction
in order to
provide the greatest strength and are placed in recessed holes so that the
bolts and nuts do
not extend past the upper and lower surfaces of the mat.
For alternative embodiments to Figure 22, the grating can instead be a metal
sheet
with apertures therein to reduce the weight of the mat. The metal sheet can be
2 inches thick
with openings both for the bolts that are used to join the mat components
together as well as
with additional openings to reduce the weight of the sheet. The openings can
be random or
uniform and can range from 1 to 6 inch in diameter for circular openings and
from 2x2 to
4x4 inch rectangular or square openings. A metal grating or welded rod
arrangement can
also be used if desired. And the metal sheet can be provided in the same size
as the mat or
like the gratings, can be made in sections that together represent the overall
size of the mat.
From the foregoing, it is seen that there are numerous combinations and
arrangements of new and useful mats that include an environmentally resistant
core
structure. Certain additional specific embodiments include the following
combinations of a
mat components:
(1) a top outer layer of elongated wood or laminated wood members; a core
construction of elongated thermoplastic boards or monolithic units of a sheet
or molded
structure, and a lower outer layer of elongated wood or laminated wood
members. The
thermoplastic boards would preferably be HDPE boards about 2 inch x 8 inch by
8 feet,
while the monolithic unit would be made of HDPE, sized 8 feet x 12, 14 or 16
feet long and
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about 2 inches thick, with a flat, closed cell or open cell geometry. The wood
members
would be about the same size as the HDPE boards.
(2) a top outer layer of elongated wood or laminated wood members; a core
construction of elongated a thermoplastic monolithic unit of a sheet or molded
structure, and
a lower outer layer of elongated thermoplastic boards. The thermoplastic would
preferably
be HDPE for the monolithic unit and/or the boards, while the boards can also
be made of an
elastomeric material which may or may not be reinforced. The size of the
monolithic unit
would be 8 feet x 12, 14 or 16 feet long and about 2 inches thick, with a
flat, closed cell or
open cell geometry, and wherein the elongated members would be about 2 inch x
8 inch by 8
feet. The wood members would be about the same size as the HDPE or elastomeric
boards.
(3) a top outer layer of elongated wood or laminated wood members; a core
construction of a grating of fiberglass reinforced thermosetting plastic
material, and a lower
outer layer of elongated wood or laminated wood members. The wood members
would have
a size of about 2 inches x 8 inches by 8 feet. The grating would be 2 inches
thick and have
openings of 2x2 inches and would be sized to match the mat, i.e., 8 feet x 12,
14 or 16 feet
long, or segments representing portions of the mat can be used (e.g., a 3, 4
or 4.5 foot long
section of an 8 foot wide mat with 4 sections used in the mat).
It is also possible to substitute environmentally resistant components for the
outer
layers of the mat although in general it is preferred to have at least one
outer layer made of
wood components. And in addition to elongated members, such components can be
sheet,
plate, grid or cellular structures, one or more of which are arranged together
to form the
length and width dimensions of the mat. The elongated members can have a
length which is
the same as that of the mat or smaller segments can be used end to end to
obtain a desired
length that conforms to that of the mat.
In addition to the preferred three layer mats, various two-layer mats are also
contemplated by the invention. This would include one layer of thermoplastic,
thermosetting, elastomeric or metal components and an outer layer of elongated
members,
typically made of wood or engineered wood although in some situations it is
possible to
instead utilize thermoplastic, thermosetting or elastomeric components,
typically as solid or
hollow components that may be filled with other materials or reinforced with
known
strengthening or stiffening additives.
The present invention provides unexpected benefits over the art in that the
outer
layer(s) can provide resistance to abrasion and abuse of the construction core
structure while
the core structure is resistant to moisture, water or even certain chemicals
encountered from
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the surrounding environment. This enables the core structure to provide a much
longer
service life than when conventional wood components are used since the core
structure is
resistant to rotting or other chemical degradation that would otherwise affect
wood
components of the core. Finally, to the extent that any of the components of
the upper or
lower outer layers are damaged, they can be replaced so that a new mat can be
made with the
reuse of all of the core.
Therefore, in sum, it is to be realized that the optimum dimensional
relationships for
the parts of the invention can include variations and tolerances in size,
materials, shape,
form, function and use are deemed readily apparent and obvious to the skilled
artisan, and all
equivalent relationships to those illustrated in the drawings and described in
the specification
are intended to be encompassed by the claims appended hereto.
Unless defined otherwise, all technical and scientific terms used herein have
same
meaning as commonly understood by one of ordinary skill in the art to which
this invention
belongs. Also, as used herein and in the appended claims, the singular form
"a", "and", and
"the" include plural referents unless the context clearly dictates otherwise.
All technical and
scientific terms used herein have the same meaning.
The foregoing detailed description is considered as illustrative only of the
principles
of the invention. Further, since numerous modifications and changes will
readily be
apparent to those having ordinary skill in the art, it is not desired to limit
the invention to the
exact constructions demonstrated. Accordingly, all suitable modifications and
equivalents
may be resorted to falling within the scope of the invention.
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