Note: Descriptions are shown in the official language in which they were submitted.
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LAMINATED SUPPORT MAT
[00011
BACKGROUND OF THE INVENTION
[0002] Various embodiments of a laminated support mat are described
herein. In particular, the embodiments described herein relate to an improved
laminated support mat and a method of manufacturing such an improved
laminated support mat.
[0003] The construction industry utilizes solid sawn wood and wood panel
members in a variety of forms to aid in the erection of buildings, roads, and
bridges. For example, temporary road panels and crane mats are often
constructed using solid-sawn hardwood timbers or some species of softwoods.
These panels are used to form a temporary lightweight roadway or foundation
to facilitate vehicular and equipment travel as may be required in
construction
operations. Other industry users of such mats include users in the field of
pipeline, utility, transportation, oil, and infrastructure.
[0004] As shown in Fig. 1, a conventional road panel, shown generally at
10, is formed by using a plurality of solid sawn timber elements 12.
Typically,
four pieces of solid sawn timber 12 are used, each having a cross-sectional
dimension ranging from about 8 inches by 8 inches to about 12 inches by 12
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inches, with a length of 16 feet. The four pieces of timber 12 are usually
bolted
together using bolts 14 to form the temporary road panel 10 having an
assembled dimension of 4 feet by 1 foot by 16 feet. Several panels may be
placed side by side over existing ground to form a temporary roadway or to
support cranes on a construction site. Ground conditions under the panels vary
greatly and may include, for example, sand, clay, wetlands, and possibly a
considerable amount of water. Another conventional wood mat utilizes smaller
dimensional lumber and utilizes nails, carriage bolts, or steel rods as a
fastening
system. All of these systems have mechanical fastening systems to transfer
stresses between components. Additionally, U.S. Patent No. 4,932,198
discloses a compound timber-metal stressed deck with metal plates inserted
between the timbers.
[0005] The hardwood panels are typically discarded at the end of the
construction project, or they may be re-used if they are in relatively good
condition. The longevity of the panels may be as little as six months to one
year, depending on the length of the construction project and the
environmental
conditions to which the panels are subjected. The wood panels are typically
untreated with preservative chemicals because of environmental concerns.
Hardwoods are typically used because of their superior wear resistance to
heavy truck and other construction equipment traffic. In addition to road
panels and crane mats, other applications for the hardwood panels include
decks over steel girders for temporary bridges, and soldier piles.
[0006] Because the timber used to form the panel 10 is expensive, the panel
is very costly. Further, the roadway formed by the panels 10 is very costly
because tens of thousands of the panels 10 may be used for a single
construction project. In addition, the solid sawn timber used to form the
panel
10 is scarce because of the solid sawn timber must be extremely long,
typically
about sixteen feet in length. Exposure to larger amounts of water or moisture
for extended periods of time causes a portion of the panel 10 to swell or
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expand. Such expansion of the panel 10 causes undesirable cupping andlor
buckling of the panel 10. Therefore, it would be desirable to provide an
improved laminated support mat for supporting heavy equipment.
SUMMARY OF THE INVENTION
[0007] The present application describes various embodiments of a
laminated support mat and its method of manufacture. One embodiment of the
laminated support mat, such as a mat suitable for supporting heavy
construction
equipment, includes a plurality of billets fastened together, each of the
billets
being made of a plurality of individual wood laminations adhesively bonded to
each other. The billets comprise a plurality of vertically oriented individual
wood laminations. The plurality of individual wood laminations has wide faces
oriented parallel to a direction of a load applied to the support mat. Each
billet
has outboard laminations and the wide faces of the outboard laminations of
each billet define a wide face of the billet. An expansion pad is disposed
between the wide faces of adjacent billets.
[0008] Other advantages of the laminated support mat and its method of
manufacture will become apparent to those skilled in the art from the
following
detailed description, when read in light of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Fig. 1 is a side perspective view of a prior art panel formed of solid
sawn timber.
[0010] Fig. 2 is a partial side perspective view of a first embodiment of a
laminated support mat.
[0011] Fig. 3 is a partial side perspective view of a billet illustrated in
Fig. 2.
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[0012] Fig. 4 is a schematic end view of the laminated support mat
illustrated in Fig. 2.
[0013] Fig. 5 is a schematic end view of the laminated support mat
illustrated in Figs. 2 and 4, showing the laminated support mat after
expansion.
[0014] Fig. 6 is an isometric side view of a second embodiment of a
laminated support mat.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Referring now to Fig. 2, a first embodiment of a laminated support
mat is indicated generally at 20. The illustrated mat 20 is comprised of a
plurality of laminated beams or billets 22. Each of the illustrated billets 22
comprises a plurality of wood members or individual wood laminations 24. If
desired, apertures 26 may be formed through the support mat 20 for receiving
fastening means, such as the bolts 28, as will be described in detail herein.
As
used in the description of the invention, the term "mat" includes mats as well
as
panels. One example of such a support mat 20 is described in co-assigned U.S.
Patent No. 7,137,226.
[0016] The individual wood laminations 24 may be fabricated by
structurally joining together arbitrary or different lengths or strips of wood
or
wood material. The arbitrary strips of wood material may be disposed end-to-
end and joined together, such as by a jointing process. One example of such a
jointing process is finger jointing. It will be understood that the strips may
be
continuous and full length. The arbitrary strips of wood may be strips of
hardwood, such as oak, birch, or maple, although any desired hardwood or
softwood may be used. The strips of wood laminations 24 may be any length,
such as a length within the range of from about 5 feet to about 16 feet. The
strips of wood material may be joined together to define the individual wood
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laminations 24 of any desired length, such as individual wood laminations
having a length of about 16 feet. It will be understood however, that the
individual wood laminations 24 may be of any other desired length. Not all the
wood laminations 24 need to be formed by joining together the strips, and the
billet may be formed with some of the laminations formed by joined strips, and
some of the wood laminations 24 being a continuous piece of full length wood.
In one embodiment of the billet 22, at least 50 percent of the wood
laminations
are made of strips joined together.
100171 As best shown in Fig. 3, the individual wood laminations 24 have a
thickness or height H 1, a thickness or width W 1, and a length L i. The
laminations 24 may have any desired length Li, such as, for example, a length
of about 12 feet. It will be understood however, that the laminations 24 may
have any other desired length. Examples of other suitable lamination lengths
Ll include 14 feet, 16 feet, 18 feet, and 20 feet. In one embodiment, the
individual wood laminations 24 have a height H1 within the range of from
about 3 inches to about 6 inches. In another embodiment, the individual wood
laminations 24 have a height H 1 of about 5%Z inches. In another embodiment,
the individual wood laminations 24 have a width W i within the range of from
about 0.50 inches to about 1.00 inches. It will be understood however, that
the
individual wood laminations 24 may have any desired height H 1, width W 1,
and length L 1.
[0018] In the embodiment illustrated in Fig. 2, a plurality of the individual
wood laminations 24 are joined together to form the laminated billets 22. The
illustrated individual wood laminations 24 are vertically oriented, having a
wide face 30 oriented parallel to a direction of a (load indicated by the
arrow
32) applied to the laminated billet 22.
[0019] The individual wood laminations 24 may be joined together into the
billet 22 using any desired adhesive. The individual wood laminations 24 may
be joined together with a waterproof adhesive, such as an adhesive that
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conforms to ASTM D2559-01. Any desired number of individual wood
laminations 24 may be joined together to form the laminated billet 22. In one
embodiment, with the range of from about 20 laminations to about 30
laminations are joined together to form the billet 22. In another embodiment,
about 261aminations are assembled together to form the laminated billet 22.
Each billet 22 includes outboard laminations 34, as shown in Fig. 3. The wide
faces of the outboard laminations 34 of each billet 22, such as the wide face
30,
define a wide face of the billet 22.
[0020] As best shown in Fig. 3, the laminated billet 22 has a height Hl, a
width W2, and a length L i. It will be understood that the laminated billet 22
may have any desired width W2. A typical laminated billet 22 may contain
within the range of from about 14 laminations to about 16 laminations~and have
a width W2 of about 12 inches. In the illustrated embodiment, the length L1 of
the laminated billets 22 is equal to the length L1 of the laminations 24, and
the
height H 1 of the laminated billets 22 is equal to the height H 1 of the
laminations 24.
[0021] A plurality of laminated billets 22 may be attached to one another by
any suitable means to form the laminated support mat 20. In the embodiment
illustrated in Fig. 2, the billets 22 are assembled together with a fastener,
such
as the bolts 28 that extend through bolt apertures 26. It will be understood
that
any other desired fastener may be used. Adhesive, binding wire, shear
connections, or brackets, all not shown, may also be used to connect the
laminated billets 22 together into the mat 20. These mechanical fastening
systems allow stresses to be transferred between components. An adhesive
may also be used in conjunction with a mechanical fastening system.
[0022] In the embodiments illustrated in Figs. 2 and 4, a plurality of
laminated billets 22 is attached to one another to form the support mat 20. In
the illustrated embodiment, the wide faces 30 of the outboard laminations 34
of
adjacent billets 22 are disposed such that a space 36, the purpose of which
will
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be described in detail below, is defined between the adjacent billets 22. The
three laminated billets 22 illustrated in Fig. 2 further defme a width W3 for
the
entire support mat 20. It will be understood that the support mat 20 may have
any desired width W3. As best shown in Fig. 2, the support mat 20 also has a
height H 1 and a length L 1. It will be understood that the support mat 20 may
have any desired width W3.
[0023] Although the embodiment illustrated in Fig. 2 includes three billets
22 and the embodiment illustrated in Fig. 4 include four billets 22, it will
be
understood that any desired number of laminated billets 22 may be attached to
one another to..form the support mat 20. Also, the laminated billets 22 need
not
all be of the same width W2, but may be of different widths W2. Examples of
suitable mat widths W3 include widths of 4 feet and 8 feet.
[0024] Although the billets 22 are shown as having individual wood
laminations 24 of a generally uniform width Wi, it will be understood that the
billets 22 may be made of individual wood laminations 24 that vary in
thickness across the width W2 of the billet 22. Also, it will be understood
that
the billets 22 on the outboard sides the mat 20 need not be identical to each
other or to the billet/billets 22 in the central portion of the mat 20.
[0025] Referring now to Fig. 6, a second embodiment of a laminated
support mat is indicated generally at 40. The illustrated mat 40 is comprised
of
a plurality of the laminated billets 22. Each of the illustrated billets 22
comprises a plurality of the individual wood laminations 24. Apertures 20 are
formed through the support mat 40 for receiving the fastening bolts 28, as
described in detail herein above.
[0026] As best shown in Fig. 6, the billets 22 may be provided with one.or
more lifting members 42 for the attachment of lifting cables, not shown. The
lifting members 42 may be positioned within recesses 44 formed at any
location along an edge 46 of the support mat 40. It will be understood that
any
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nuinber of recesses 44 and/or lifting members 42 may be provided on the edges
46 of the mat 40. It will be further understood that the recesses 44 may be
formed at any location along the edges 46 of the support mat 40.
[0027] Referring again to Fig. 3, an embodiment of an expansion pad is
indicated generally at 50. In the illustrated embodiment, a plurality of the
expansion pads 50 is shown disposed on the wide faces 30 of the outboard
laminations 34, and within the space 36 between adjacent billets 22. It will
be
understood that any number of pads 50 may be disposed within the space 36
between adjacent billets 22, such as for example, one pad 50.
[0028] The plurality of expansion pads 50 may be positioned having any
desired distance between adjacent pads 50. In the illustrated embodiment, a
center 52 of each expansion pad 50 is spaced a distance D from the center 52
of
an adjacent expansion pad 50. In one embodiment, a center 52 of each
expansion pad 50 is spaced about 24 inches from the center 52 of an adjacent
expansion pad 50. Alternatively, the expansion pads 50 may be spaced at any
desired distance from one another. If desired, the pads 50 may be secured by
any suitable means to the wide faces 30 of the outboard laminations 34 prior
to
the billets 22 being assembled together with the bolts 28. Examples of
suitable
means to secure the pads 50 to the wide faces 30 of the outboard laminations
34 include staples 51, nails, adhesive, and the like.
[0029] In the illustrated embodiments, the pads 50 are positioned such that
the bolts 28 extend through an aperture at the center 52 of the pads 50. It
will
be understood that the mat 20, 40 may be assembled such that the bolts 28
extend through any desired portion of the pads 50, extend through only a
portion of the pads 50, or do not extend through any pads 50.
[0030] The expansion pad 50 may have any desired thickness or width W4.
In one embodiment of the expansion pad 50, the pad 50 has a width W4 within
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the range of from about 0.375 inches to about 0.625 inches. In another
embodiment of the pad 50, the pad 50 has a width W4 of about 0.375 inches.
[0031] The expansion pad 50 may have any desired length L2. In one
embodiment of the expansion pad 50, the pad 50 has a length L2 within the
range of from about 3 inches to about 12 inches. In another embodiment of the
pad 50, the pad 50 has maximum length L2 of about 12 inches.
[0032] The expansion pad 50 may have any desired height H2. In one
embodiment of the expansion pad 50, the pad 50 has a height H2 within the
range of about 70 percent to about 80 percent of the height H 1 of the wide
face
30 of the billet 22. In another embodiment of the pad 50, the pad 50 has a
height H2 of about 75 percent of the height H 1 of the wide face 30 of the
billet
22.
[0033] The expansion pad 50 may be formed from any desired material
having the properties of good mechanical strength, high ozone and weather
resistance, good aging resistance, low flammability, good resistance toward
chemicals, moderate oil and fuel resistance, and adhesion to many substrates.
One embodiment of a material for the expansion pad 50 has a shore A hardness
(shore A hardness is the relative hardness of elastic materials, typically
determined with a Shore A durometer) within the range of from about 40 to
about 50, an elongation at rupture within the range of from about 100 percent
to about 70 percent, and a moderate resistance to weathering, ozone, gas,
diesel, mineral oil, and hydraulic fluid. Examples of suitable materials for
the
expansion pad 50 include chloroprene or polychloroprene (CR) rubber, and
natural rubber.
[0034] In the embodiment illustrated in Fig. 4, the support mat 20 is
substantially symmetrical and includes a first support surface 54 (upwardly
facing as viewed in Fig. 4) and a second support surface 56 (downwardly
facing as viewed in Fig. 4) opposite the first support surface 54. Each of the
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first and second support surfaces 54 and 56 define a substantially flat
surface.
Accordingly, either of the first and second support surfaces 54 and 56 may be
placed against a surface, such as the ground, at a construction site. The
other of
the first and second support surfaces 54 and 56 thereby faces upwardly to
support objects, such as vehicles, equipment, and the like.
[0035] When only a portion of the support mat 20, such as a region 58
adjacent only one support surface (such as the second support surface 56
illustrated in Fig. 5) experiences prolonged exposure to 'water or other
moisture
over a period of time, swelling or expansion of the support mat 20 may occur
asymmetricallyr As a result of such asymmetrical expansion, the region 58
adjacent only one support surface (the second support surface 56 in the
illustrated embodiment) expands substantially as shown in Fig. 5. It will be
understood that the period of time that the support mat 20 must be exposed
water or other moisture before the illustrated expansion occurs may vary based
on the type of wood and/or laminates used and the environmental conditions
extant at the site the mat 20 is used. Typically, such expansion of the region
58
may occur a$er the region 58 of the mat 20 has been continuously submerged
in water for within the range of from about two weeks to about 3 weeks.
[0036] The expansion pads 50, disposed between each adjacent billet 22,
permit the asymmetrical expansion of the billets 22 in the region 58, while
preventing the support mat 20 from undesirably cupping and/or buckling and
thereby allowing the first and second support surfaces 54 and 56 to remain
substantially flat. As the region 58 of the billets 22 expand, the pads 50 are
compressed inwardly (as indicated by the arrows 64 in Fig. 5) such that
portions of the pad 50 are caused to extend upwardly and downwardly (as
viewed in Fig. 5). The pads 50 may extend upwardly and downwardly
substantially to or near the first and second support surfaces 54 and 56, as
shown at 60 in Fig. 5. Alternatively, portions of the pad 50 may be caused to
extend upwardly and downwardly (as viewed in Fig. 5) through only a portion
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of the distance to the first and second support surfaces 54 and 56, as shown
at
62 in Fig. 5.
[0037] Advantageously, a mat, such as the illustrated embodiment of the
mat 20, having the expansion pads 50 disposed between each adjacent billet 22,
has been shown to substantially eliminate cupping andlor buckling of the mat
20 after prolonged exposure to water.
[0038] Use of the pads 50 as described herein has been shown to be
particularly effective in substantially eliminating cupping and/or buckling in
mats having an aspect ratio greater than 13. As used herein, aspect ratio is
defined as:
support mat width W3support mat height Hl.
It will be understood however, that the pads 50 may be used and effective in
substantially eliminating cupping and/or buckling in mats having an aspect
ratio of 13 or less.
[0039] Another advantage of the embodiments of the support mat 20
described herein is that the laminated billets 22 have an allowable design
strength value greater than about 3000 psi. Bending strength is measured,
destructively, using a four-point bending test apparatus such as described in
ASTM D198-00, with the wide face of the laminations parallel to the direction
of applied load. Such a design strength value greater than about 3000 psi is
superior to known sawn timber billets which typically have a strength value
within the range of from about 650 psi to about 700 psi.
[0040] Another advantage of the embodiments of the support mat 20
described herein is that the support mat 20 has a smaller height H 1 relative
to
known wood mats, such as the prior art mat 10 in Fig. 1. The support mat 20 is
thereby easier to move and to store, requires a smaller amount of wood
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material, and efficiently uses raw material resources to make the mat less
costly.
[0041] Another advantage of the embodiments of the support mat 20
described herein is that the mats 20 may be made with a tailor-made strength
profile for particular strength applications. Further, raw material defects
such
as knots will be well distributed throughout the structure because each knot
will
have a thickness that is no thicker than the width W1 of the laminations 24.
The width W 1 of the laminations 24 is relatively small when compared to the
thickness or width W2 of the laminated billet 22.
[0042] Yet another advantage of the embodiments of the support mat 20
described herein is that the support mat 20 has a weight that is within the
range
of from about 25 percent to about 60 percent lighter than prior art mats
having
the same surface area, such as for example, the mat 10. In the embodiment
illustrate in Fig. 2 for example, the weight of the support mat 20 is about 50
percent of the weight of a prior art mat having the same surface area, such as
the mat 10.
100431 In another embodiment of the support mat 20, some or all of the
individual wood laminations 24 may be reinforced with a reinforcement
material to make them capable of withstanding greater loads. The
reinforcement material may be any material suitable for improving the strength
of the overall billet 22 and the mat 20. For example, a layer of woven or
nonwoven fiberglass strands, steel, or other metals and non-metals may be
applied between adjacent laminations 24 and/or between adjacent billets 22.
[0044] The principle and mode of operation of the laminated support mat
and its method of manufacture have been described in its various embodiments.
However, it should be noted that the laminated support mat and its method of
manufacture described herein may be practiced otherwise than as specifically
illustrated and described without departing from its scope.
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