Note: Descriptions are shown in the official language in which they were submitted.
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HYBRID CRANE MATS WITH LIFTING ELEMENTS
CROSS-REFERENCE TO RELATED APPLICATIONS (for US National Stage)
This application is a continuation-in-part of US application Ser. No.
15/400,951 filed
Jan. 6, 2017, which is a continuation-in-part of US application Ser. No.
15/377,545 filed
Dec. 13, 2016, which is a continuation-in-part of US application Ser. No.
15/244,614 filed
Aug. 23, 2016, which is a continuation-in-part of US application Ser. No.
15/188,113 filed
Jun. 21, 2016, which is a continuation-in-part of US application Ser. No.
15/155,685 filed
May 16, 2016, which is a continuation-in-part of US application Ser. No.
15/081,340 filed
Mar. 25, 2016, now US Pat. No. 9,476,164, which is a continuation-in-part of
US application
Ser. No. 15/056,212 filed Feb. 29, 2016, now US Pat. No. 9,447,547, which is a
continuation-
in-part of US application Ser. No. 14/839,888 filed Aug. 28, 2015, now US
patent 9,315,949,
which claims the benefit of each of US application Ser. Nos. 62/054,186 filed
Sep. 23, 2014,
62/138,143 filed Mar. 25, 2015, and 62/158,196 filed May 7, 2015.
US application Ser. No. 15/244,614 filed Aug. 23, 2016 claims the benefit of
application no. 62/211,664 filed August 28, 2015.
This application is also a continuation-in-part of application Ser. No.
15/331,130 filed
Oct. 21, 2016, which is a division of US application Ser. No. 15/155,685 filed
May 16, 2016,
which is a continuation-in-part of US application Ser. No. 15/081,340 filed
Mar. 25, 2016,
now US Pat. No. 9,476,164, which is a continuation-in part of application Ser.
No. 15/056,212
filed Feb. 29, 2016, now US Pat. No. 9,447,547, which is a continuation-in-
part of application
Ser. No. 14/839,888 filed Aug. 28, 2015, now US Pat. No. 9,315,949, which
claims the
benefit of each of application Ser. Nos. 62/054,186 filed Sep. 23, 2014,
62/138,143 filed Mar.
25, 2015, and 62/158,196 filed May 7, 2015.
Each of the foregoing applications is expressly incorporated herein by
reference
thereto.
BACKGROUND
The present invention relates to new, hybrid crane mats that have lifting
elements for
movement and installation of crane mats. These mats are typically used in
construction sites
that require heavy lifting, crane support stabilization, temporary areas for
installation of
pipelines or bridges, and other support structures in locations where the
ground requires
grading and stabilization to provide a flat support surface for such equipment
or activities.
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Conventional industrial mats are typically 4 feet wide and utilize beams
having square
or rectangular cross sections of sizes between 8x8 inch to 16x16 inch that are
up to 40 feet in
length that are connected by joining members or carriage bolts. Typically, the
beams 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
available from Quality
Mat Company, Beaumont, Texas. These mats, which are often called timber mats
or crane
mats. There are concerns regarding the lifting and movement of such mats due
to their
relatively large sizes.
In the past, lifting, manipulation and placement of the mats were facilitated
by
exposing part of the joining member for grasping by a lifting hook of a crane
or other heavy
piece of equipment. While the exposure of the joining or connecting rod
facilitated lifting or
moving operations, it presented an issue in that workers could inadvertently
step into over the
open hole that was provided around the connecting rod. Also, the larger sizes
of these mats
require lifting elements that facilitate overhead lifting elements. Thus,
other designs are
.. needed to more easily move these large mats as well as to provide greater
safety to personnel
working on these mats. Also, it is desirable to have improvements in the
construction of such
mats to provide extended service lives and better performance in use.
SUMMARY OF THE INVENTION
The present invention now satisfies these needs in the art by providing new
crane mats
with improved properties as well having newly designed and improved lifting
elements and
associated structures and arrangements for lifting and manipulation of these
crane mats.
These lifting elements, structures and arrangements also provide a lower
profile where the
lifting elements are maintained below the working surface of the mat to
promote safety for
workers. Also, the mat construction enables the use of lower cost core
materials that are
protected by a metal frame which in turn is protected by various outer boards,
beams and/or
bumper members.
The lifting elements are designed for use on a crane mat that has a working
surface, a
plurality of longitudinal members, and an opening or recess for receiving the
lifting element.
This lifting element comprises a loop portion that is configured with an
opening sufficient to
receive and allow grasping by a hand, fingers, or a hook or other lifting
member; a support
member for supporting the loop portion; and a securement portion for securing
the lifting
element to the mat; wherein the loop portion, support member and securement
portions are
connected to each other and wherein the support member is secured to the
opening or recess in
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the mat. The opening is configured and dimensioned to have a floor for
receiving the support
member, a channel for receiving the securement portion, and a depth that
allows the lifting
element to be received in the opening with the loop portion in a storage
position that is
maintained at or below the working surface of the mat when not used for
lifting or moving of
the mat or for securing articles thereto. Thus, the support member and
securement portion are
fixed in the mat while the loop portion is movable to a lifting position that
exposes the loop
above the working surface of the mat for engagement by a hook or other
grasping element for
certified overhead lifting, manipulation or movement of the mat or for
securing other articles
to the mat.
The lifting element generally has a body member for joining the loop and
securement
portions, wherein the body member extends in the channel and into the mat away
from the
support member, and is fixed in position by the support member and securement
portion. In
one embodiment, the body member comprises an elongated rod that passes through
the mat
from the working surface to the opposite side, the support member is a head
portion of the
.. elongated rod that has openings for receiving and securing the loop portion
thereto, and the
securement portion comprises a threaded end of the rod member and a fastening
nut, such that
the lifting element is secured to the mat with the head and loop portions
provided in the
opening and with the nut present in an opening or recess on the opposite side
of the mat from
the working surface. If desired, the lifting element can include a first
contact plate present
between the head portion and the floor of the opening; a second contact plate
between the nut
and the recess; or both first and second contact plates so that the lifting
element is more
securely attached to the mat.
In another embodiment, the loop portion of the lifting element is a ring
member that is
secured to the support member in a manner that allows the ring to pivot
between the storage
and lifting positions, the body member comprises a first plate that passes
into the mat, the
support member has a thickness that is greater than that of the first plate
with the body and
support members fixed in position in the mat, and the mat includes lateral
rods for joining
together the longitudinal members and the securement portion includes an
opening in the first
plate sufficient to receive therein one of the lateral rods of the crane mat
to attach the lifting
element to the mat.
In yet another embodiment, the body member of the lifting element comprises a
first
plate that passes into the mat, the support member is a second plate oriented
perpendicular to
the first plate, wherein the support member plate includes holes to receive
fasteners that secure
the support member plate to the floor of the opening or recess, wherein the
mat includes
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lateral rods for joining together the longitudinal members and the securement
portion includes
an opening in the first plate sufficient to receive therein one of the lateral
rods of the crane mat
to attach the lifting element to the mat. Preferably, the loop portion is a D-
ring that is attached
to the support member by a U-shaped member that is welded to one side of the
second plate,
and the body member is welded to the opposite side of the second plate. Also,
the recess in
the mat preferably has a depth that is only slightly larger than the ring
member of the lifting
element in order to minimize the open area of the recess to facilitate removal
of dirt or foreign
debris therefrom.
Other embodiments are disclosed in the detailed description.
Generally, between 2 and 12 lifting elements are provided in the mat,
preferably in a
symmetrical pattern. The openings or recesses for at least two of the lifting
elements are
spaced about 1 to 3 feet from the front or rear ends of the mat so as to
provide easy access by
the crane or lifting device.
The invention also provides a crane mat having a working surface and an
opening or
recess in the working surface. The crane mat is designed for overhead lifting
and comprises
outer side members comprising first and second side beams or boards of
engineered lumber,
oak or other hardwoods, or bumper members of solid or filled or unfilled
hollow plastic
members that optionally may be reinforced; a core structure comprising a
plurality of
longitudinal members; a plurality of joining rods that attach the outer side
members to the
longitudinal members of the core structure; and one or more lifting elements
comprising a
loop portion that is configured with an opening sufficient to receive and
allow grasping by a
hand, fingers, or a hook or other lifting member, a support member for
supporting the loop
portion, and a securement portion for securing the lifting element to the mat,
wherein the loop
portion, support member and securement portions are connected to each other.
Advantageously, the opening is configured and dimensioned to have a floor for
receiving the
support member, a channel for receiving the securement portion, and a depth
that allows the
lifting element to be received in the opening with the loop portion in a
storage position that is
maintained at or below the working surface of the mat when not used for
lifting or moving of
the mat or for securing articles thereto, wherein the support member is
secured to the floor of
the opening or recess with the securement portion fixed in position in the
mat. Also, the loop
portion is movable to a lifting position that exposes the loop above the
working surface of the
mat for engagement by a hook or other grasping element for certified overhead
lifting,
manipulation or movement of the mat or for securing other articles to the mat.
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Preferably, the upper surfaces of the longitudinal members form at least part
of the
working surface of the mat, wherein the opening or recess is present in one or
adjacent
longitudinal members, and wherein the mat optionally includes metal plates of
the same
height and length as the longitudinal members and which are provided between
adjacent
longitudinal members. The crane mat may further comprise external components
including an
upper layer of elongated members located above and attached to the core
structure to protect
the core structure, a lower layer of elongated members located below and
attached to the core
structure to also protect the core structure, or both of the upper and lower
layers. These
elongated members are made of wood, engineered wood, metal or a thermoplastic,
thermosetting plastic, or elastomeric material, wherein each lifting element
is located in an
opening that is at least partially present in an elongated member of the upper
or lower layer
and a subjacent longitudinal member or present in adjacent elongated and
longitudinal
members, with each lifting element connected to a joining rod to secure the
lifting element to
the mat.
The preferred lifting element further comprises a body member for joining the
loop
and securement portions, wherein the body member extends in the channel and
into the mat
away from the support member, and is fixed in position by the support member
and
securement portion, wherein the securement portion includes an opening
sufficient to receive
a joining rod therein, and with a joining rod passing through the securement
portion to attach
the lifting element to the mat.
When the core structure of the mat further comprises a metal frame that
includes side
and end members, and when the outer side members, side members of the frame
and
longitudinal members each include a plurality of spaced lateral apertures
passing
therethrough, with the lateral apertures being in alignment to form bores
through the mat; each
joining rod will pass through each of the previously mentioned members through
the aligned
lateral apertures and bores to hold the members together in the mat.
Additionally, it is
possible for the lifting element to be directly attached to the metal frame by
welding.
Additional crane mat structures are disclosed herein and in the documents that
are
incorporated by reference herein.
BRIEF DESCRIPTION OF THE DRAWINGS
The nature and various advantages of the present invention will become more
apparent
upon consideration of the following detailed description, taken in conjunction
with the
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accompanying drawings, in which like reference characters refer to like parts
throughout, and
in which:
Figure 1 is a perspective view of a first embodiment of a crane mat having new
lifting
elements according to the present invention;
Figure 2 is an exploded view of the mat of Figure 1 to illustrate the various
components present therein;
Figure 3 is a top view of a first embodiment of a lifting element for use in
the present
invention;
Figure 4 is a side view of the lifting element of Figure 3;
Figure 5 is a front view of the lifting element of Figure 3;
Figure 6 is a perspective view of the lifting element of Figure 3;
Figure 7 is a cross sectional view taken through the crane mat of Figure 1
along one of
the longitudinal members to show the arrangement of the internal and external
members;
Figure 8 is a perspective view of a second embodiment of a crane mat having
new
lifting elements according to the present invention;
Figure 9 is an exploded view of the crane mat of Figure 8 to illustrate the
various
components present therein;
Figure 10 is a perspective view of a third embodiment of a crane mat having
new
lifting elements according to the present invention;
Figure 11 is an end view of the crane mat of Figure 10;
Figure 12 is a perspective view of a fourth embodiment of a crane mat having
new
lifting elements according to the present invention;
Figure 13 is an expanded view of the front end of the crane mat of Figure 12
with one
of the longitudinal members removed to illustrate the connection of the
lifting element;
Figure 14 is a cross sectional view taken through the crane mat of Figure 12
to
illustrate the position of the lifting element in use;
Figure 15 is an exploded view of a fifth embodiment of a crane mat having an
internal
frame to illustrate the various components present therein;
Figure 16 is an exploded view of the frame member of the crane mat of Figure
15 to
illustrate the attachment of the cross members;
Figure 17 is an end view of a sixth embodiment of a crane mat having new
lifting
elements according to the present invention;
Figure 18 includes Figures 18A and 18B which are a partial sectional views of
the
lifting element of the crane mat of Figure 17 in operative and storage
positions, respectively;
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Figure 19 includes Figures 19A and 19B which are a partial sectional views of
a
variation of the crane mat of Figure 17 with the lifting element in operative
and storage
positions, respectively.
Figure 20 is a front view of another lifting element for use in the present
invention;
Figure 21 is a side view of the lifting element of Figure 20;
Figure 22 is a side view of the lifting element of Figure 20 in a storage
position;
Figure 23 is a side view of the lifting element of Figure 20 in use;
Figure 24 is a front view of another lifting element for use in the present
invention;
Figure 25 is a side view of the lifting element of Figure 24;
Figure 26 is a perspective view of a crane mat having a core construction of
pine
timbers that are protected by oak beams and boards;
Figure 27 is an exploded view of the crane mat of Figure 26 to illustrate the
various
components of the mat;
Figure 28 is a partial perspective view of the end of the crane mat of Figure
26;
Figure 29 is a partial perspective view of the end of the crane mat of Figure
26 with
certain outer components removed to better illustrate the internal components
of the mat;
Figure 30 is a perspective view of another embodiment of a mat according to
the
present invention;
Figure 31 is an exploded view of the mat of Figure 30 to illustrate the
various
components present therein;
Figure 32 is a perspective view of the support structure for the mat of Figure
30;
Figure 33 is a perspective view of yet another embodiment of a mat according
to the
present invention;
Figure 34 is a partial sectional view of the support structure for the mat of
Figure 33;
Figure 35 is an exploded view of the collar members for the openings in the
elongated
members;
Figure 36 is a perspective view of the collar members in place on a mat;
Figure 37 is a perspective view of two alternative lifting members;
Figure 38 is a side cross-sectional view of the lifting elements of Figure 37
in their
normal, non-use position;
Figure 39 is a side cross-sectional view of the lifting elements of Figure 37
in their
operative position during lifting of the mat;
Figure 40 is a perspective view of a crane or pipeline mat according to the
present
invention; and
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Figure 41 is an exploded view of the crane or pipeline mat of Figure 40.
DETAILED DESCRIPTION OF THE INVENTION
The new and improved crane mats of the present invention now provide a number
of
surprising advantages over conventional crane mats. The provision of a one or
more lifting
elements that are securely attached to these mats facilitates overhead lifting
and manipulation
of the mats in a much more secure manner. By securing the lifting element
directly to the
joining rod of the mat, the weight of the mat becomes directly distributed
from the mat onto
the joining rod to the lifting element. Prior crane mats included a large
opening to expose the
joining rod to enable a crane hook to access the rod for lifting. The
provision of the lifting
elements of the present invention now provides much smaller recesses and
openings compared
to conventional crane mats to avoid having workers operating on the upper
surface of the mat
from tripping over or stepping into the hole. In addition, the recesses and
holes are sized and
configured to receive the lifting element when not in use to provide
essentially a flat in
uniform top surface of the mat in the area where the lifting element is
located, yet still allow
the loop portion of the lifting element to be simply and easily accessed and
exposed when the
mat needs to be moved.
Another advantage of the present invention is that the lifting element is
configured
such that when the loop portion is exposed above the working surface of the
mat, it also can
be used to tie down equipment, tents, or other items to the mat to stabilize
and secure such
items to prevent movement during use.
Certain terms that are used herein are defined hereinbelow to assist in the
understanding of the invention.
The term "crane mat" is intended to cover relatively large mats made primarily
of
longitudinal beams or timbers 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 6x6 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 and
typically of oak.
The term "non-wood" to describe the longitudinal beams or 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
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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.
Additionally, all dimensions recited herein are approximate and can vary by as
much
as 10 % to in some cases 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 outer top and bottom surfaces of the mat are deemed to be the working
surfaces of
the mat. Generally, the mat can have different upper and lower surfaces
recognizing that one
surface faces the ground while the other is used as a road, platform or other
working surface,
but preferably, the upper and lower surfaces are the same so that either
surface can be faced
downward with the opposite surface used for supporting equipment or allowing
movement on
the mat. Also, the surfaces are preferably made with symmetry as to the
lifting elements to
facilitate efficient lifting of the mats.
A wide variety of lifting elements can generally be provided by the invention.
Typically, the lifting element can include D-shaped members, 0-shaped members,
U-shaped
members, eyelets, hooks, circular or polygonal rings, chains, or cables. These
elements
generally have a unitary structure that can provide the necessary strength and
versatility in
allowing the mats to be certified for overhead lifting to facilitate pick up,
delivery, installation
and reclamation of the mats. Each lifting element has a strength rating of
from 1/2 ton to 12
tons depending upon the size of the mat.
All of the elements have a component that includes a loop portion that is
generally an
opening or open area in the lifting element that can be grasped by a hook or
other member of a
crane or similar lifting device. The elements also include a further
securement portion, again
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in the form of an opening or open area that allows the lifting element to
receive a joining rod
therethrough so that the lifting element is securely attached to the mat.
The number of lifting elements can vary based on the size of the mat. At least
one
lifting element is provided on each of the top and bottom surfaces of the mat
when
symmetrical mats having the same top and bottom surfaces are provided. It is
also possible to
have two lifting elements in the center of the mat near each end as shown in
Figure 1. Greater
numbers of lifting elements can be used with 4 or even 8 or 12 lifting
elements on each
surface of the mat. These can be arranged symmetrically in the mat surface to
facilitate access
by the lifting device.
The lifting elements are located in recesses which can be provided between
adjacent
beams or if desired, within the beams. As noted, the recesses can be arranged
horizontally and
parallel to the working surface of the mat, or vertically and perpendicular to
the working
surface of the mat. The specific arrangement is determined based on the type
of lifting
element that is to be used. Additionally, the recesses can be provided in
adjacent beams while
also located in or over the spacing between the beams.
In the most preferred arrangement the recesses are rectangular in
configuration and
shape but other configurations and shapes can be used. For example, sloped
walls of the
recess can be provided to create a V shape for the vertical embodiment while
the horizontal
embodiment can vary based on the shape of the support plate and can be round,
oval or other
.. polygonal shapes other than rectangular or square.
To prevent movement of the lifting element in the horizontal embodiment, the
support
plate can include a number of openings for nails, bolts or screws to more
firmly attach the
lifting element to the mat. The support plate can include 2, 3, 4 or more
openings depending
upon the size of the mat and lifting element. These help prevent any movement
of the lifting
.. element during movement of the mat except of course of the loop member.
The preferred embodiments for the lifting elements include a D- or 0-shaped
member
that can pivot from a horizontal position, where it can be stored beneath the
working surface
of the mat, to a lifting position where the D- or 0-shaped member is exposed
for grasping by a
hook member of a crane or other equipment. Other rings or plate members that
have arcuate
.. ends or edges and that include the appropriate opening or openings can be
used.
Other suitable lifting elements includes chains one end of which is secured or
attached
to a joining rod and the other end of which includes a chain link or other
loop portion for
engaging a crane hook for lifting of the mat. The chain is retained in the
recess when in the
storage position. The chain is configured of steel having sufficient strength
to be able to lift
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the entire mat without bending or breaking. Also, the links at either end of
the chain can be
securely attached to the joining rod when the mat is assembled.
In a preferred arrangement, only one end of the chain is permanently secured
to the
joining rod, while the other is attached by a conventional connectable link.
Thus, after the mat
is moved into position, the chain can be disconnected and stored inside
support structure so
that personnel working on the mat will not trip over the chain.
Alternatively, if a removable chain is desired, such as may be supplied with
the
equipment used to move the mats, the chain can be provided with a connectable
link on each
end so that the workers can attach each end of the chain to the joining rod
when the mat is to
be moved. After the mat is installed, however, the chain can be removed from
the joining rod
and reused for moving or installing other mats. This again provides greater
safety for workers
as the chains are not present on the surface of the mat during use.
For additional safety, the size of the opening that receives the chain is
reduced
compared to mats of the prior art. As the opening provided for connecting the
chain is much
smaller than the previous opening or cut away beam that exposed the joining
rod, personnel
who are working or conducting operations upon the mat have a much lower chance
of
stepping into hole.
Instead of a chain, a suitable cable can be provided. This is often
constructed of metal
strands for greatest strength. Also, when cables or chains are to be used,
they should have at
least three drop forged clamps. Cable can 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.
The mat is typically made of longitudinal members having a rectangular cross-
section
with all members having the substantially the same dimensions. In an
alternative
embodiment, some or all of the beams can be made smaller than the desired
thickness of the
mat and can be protected on their top and bottom surfaces by elongated members
of boards or
other structural components. These beams are typically made of lower cost
materials having
sufficient strength for use in the mat but that may not have sufficient
ruggedness for the
intended use of the mat. In this arrangement, the protective members and
components are
selected to provide better impact and abrasion resistance than the smaller
beans such that the
strength of the beams can be obtained with mat surfaces that are more
resistant to the
movement and placement of equipment across or onto the mat.
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In a preferred embodiment, the beams are made of wood with oak or other
hardwoods
being preferred. For the embodiments where the upper and lower surfaces are
protected by
boards or other elongated members or components, the beams can be made of pine
or other
softwoods and the boards can be made of oak or other hardwoods, plastics,
elastomers or even
metal. The beams and outer boards can each be made of materials that are not
wood if
desired. Accordingly, the invention provides many different materials and
combinations that
can be used for different applications.
When the longitudinal beams are made of non-wood materials of metals, plastics
or
elastomers or combinations thereof, timber resources are conserved rather than
being
harvested to provide the long length beans for construction of the mats. It is
possible to use
wood only for the outer side beams with a support structure providing the
remaining width of
the mat. For the arrangements where the beams are of smaller dimensions than
the thickness
of the mat, further conservation of wood resources is achieved with the inner
beams protected
by upper, lower or upper and lower layers of elongated materials of any of the
materials
mentioned. This is particularly advantageous when the smaller beams are made
of pine or
other softwoods with the upper and/or lower layers of one or more boards,
plates or other
elongated members being made of a more durable material to protect the
softwood beams that
are used in the core of the mat.
And other variations are possible. The side beams can be made of a plastic,
elastomeric or metal materials. These are generally rectangular in cross
section and have a
height that is the same as the overall thickness of the mat. They can be made
as a solid
member, a tubular member that is open or filled, or as flat sheets or strips
that are layered
vertically and are attached to the mat by the rod members. If desired, steel
plates can be
interspersed between some or all of the side beam layers.
When the smaller beams in the core are protected by the upper and lower layers
of
other boards the working top and bottom surfaces of the mat are configured to
be substantially
uniform. In one arrangement, the top or bottom surfaces of the mat includes
the top or bottom
surfaces of the side beams and of the boards that protect the core beams. And
in other
arrangements, all beams can be of the same height with the upper and lower
layers of boards
covering all beams. In this arrangement, the top and bottom surfaces of the
mat are the top
and bottom surfaces of the protective boards.
A preferred embodiment uses fiberglass reinforced thermosetting resins,
generally in
the form of a pultrusion, for the side beams, all internal beams or the
support structure, and for
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the elongated members essentially eliminates the use of any wood in the mats.
This further
conserves timber resources.
The use of a non-wood core or 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. This also reduces
the demand
for wood beams or elongated members in particular by 50 to as much as 100%.
The mats of the invention typically include a plurality of longitudinal beams
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 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.
The beams are typically made of any type of wood with oak being the most
preferred.
They 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. As oak becomes
more
difficulty to obtain, eucalyptus grandis trees have been harvested to provide
the necessary
length of beams, timbers, and elongated members. This species is commonly
known as the
flooded gum or rose gum, is a tall tree with smooth bark, rough at the base
fibrous or flaky,
grey to grey-brown. At maturity, it reaches 50 to 80 meters tall so that it
can easily provide
the long lengths needed for the larger mats. Additionally a layered veneer
laminate can also
be used for these members or beams. It is expected that the cost for these new
wood materials
would be about the same as the price for oak thus making them attractive
alternatives.
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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", in widths from about 2 inches to 54", and in lengths of
about 8 feet to 64
feet; and
- layered veneer laminate (LVL) which is also a billet that can be made up
to about 4
feet square by any length.
Alternatively, the beams 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 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.
While the beams are typically made of wood, as noted other materials may
instead be
used. When the beams 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
beams 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
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lower tendency to rust when contacted by moisture. It is preferred that the
metal be weldable
to facilitate construction of the beams.
Aluminum or titanium can also be used for the beams in specialty applications.
All of
these materials generally have higher cost than steel and some present greater
difficulties
during welding or brazing.
The metal beams are typically provided as square or rectangular tubular
structures or
as a plurality of plates. These members can be prepared in the desired shape
and
configuration by welding smaller shapes or segments together.
Alternatively, the beams 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 which may be
hollow or filled
with other materials depending on the overall weight and compressibility
desired for the
construction.
The plastic or elastomeric materials can be used either as solid rectangular
structures
.. or as layers with or without interleaving steel plates. Depending upon the
anticipated service
and conditions to be experienced, different combinations of beam materials can
be used.
Thus, the invention provides a wide range of different beam materials and
material
combinations that can be selected for any particular end use or service
requirement for 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 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.
A plurality of joining members are used to secure the beams together. These
joining
rods are typically large rods or 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. These rods or carriage bolts are
typically made of a
high strength steel.
In a preferred embodiment, the crane mat comprises outer side members
comprising
first and second side beams or boards of engineered lumber, oak or other
hardwoods, or
bumper members of solid or filled or unfilled hollow plastic members that
optionally may be
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reinforced; a core structure comprising a metal frame that includes side and
end members and
that contains therein a plurality of longitudinal members made of pine or
other softwoods;
external components including an upper layer of elongated members located
above and
attached to the core structure to protect the core structure, a lower layer of
elongated members
located below and attached to the core structure to also protect the core
structure, or both of
the upper and lower layers; and a plurality of j oining rods that attach the
outer side members
to the core structure. The elongated members are advantageously made of wood,
engineered
wood, a metal such as steel, or a thermoplastic, thermosetting plastic, or
elastomeric material,
including recycled plastic materials.
The outer side members, side members of the frame and longitudinal members
each
generally include a plurality of spaced lateral apertures passing
therethrough, with the lateral
apertures being in alignment to form bores through the mat; wherein each
joining member
passes through each of the previously mentioned members through the aligned
lateral
apertures to hold the members together in the mat. Preferably, the mat further
comprises steel
plates of substantially the same height as the pine timbers with each plate
located between
adjacent pine timbers, wherein the joining rods also pass through the steel
plates to hold those
components together in the mat.
The crane mat advantageously includes one or more lifting elements each
located in an
opening in that is at least partially present in an elongated member of the
upper or lower layer
and a subjacent longitudinal member or present in adjacent elongated and
longitudinal
members of the upper or lower layer, with each lifting element connected to a
joining rod to
secure the lifting element to the mat; and with the lifting element(s)
comprising a loop portion
that is configured with an opening sufficient to receive and allow grasping by
a hook, fingers,
hand or other lifting member, and a securement portion that includes an
opening sufficient to
receive a joining member therein, with the loop and securement portions either
connected to
each other or forming a unitary lifting element, and with a joining member
passing through
the securement portion to attach the lifting element to the mat.
The opening is preferably configured and dimensioned to receive the lifting
element
therein in a storage position with the lifting element maintained at or below
the surface of the
mat when not used for lifting or moving of the mat or when securing articles
thereto, and
wherein the loop portion is movable to a lifting position that exposes the
loop above the
surface of the mat for engagement by a hook or other grasping element for
certified overhead
lifting, manipulation or movement of the mat or for securing other articles to
the lifting
element.
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Alternatively, the frame member may further comprise one or a plurality of
cross
members attached to side members to strengthen the frame, with the
longitudinal members
located between cross members and with additional filler members located
between the cross
members and end members of the frame, wherein a joining member passes through
the
additional filler members through aligned lateral apertures therein to hold
those members
together in the mat. One or more lifting elements can be included, again with
each located in
an opening in that is at least partially present in an elongated member of the
upper or lower
layer and a subjacent longitudinal member or present in adjacent elongated and
longitudinal
members of the upper or lower layer, with each lifting element connected to a
cross member
to secure the lifting element to the mat.
The crane mat preferably includes outer end members to protect the end members
of
the frame, the outer end members comprising first and second side beams of
engineered
lumber, oak or other hardwoods, or bumper members of solid or filled or
unfilled hollow
plastic members that optionally may be reinforced. Also, the side and end
members of the
frame are preferably made of steel C-beams that retain the longitudinal
members
therebetween.
The working surfaces of the mat can be configured in different ways. In one
arrangement, the outer side members each have a top surface and is located in
a position that
aligns the top surface of each outer side member with the upper surfaces of
the elongated
members of the upper layer to form an upper working surface for the mat.
Additionally, the
outer side members each also may have a bottom surface and is located in a
position that
aligns the bottom surface of each outer side member with the lower surfaces of
the elongated
members of the lower layer to form a lower working surface for the mat.
Alternatively, the
elongated members of the upper or lower layers extend across the entire width
and length of
the mat including over the outer side members to form a working surface for
the mat.
For the lifting elements, the loop portion preferably is a D- or 0-shaped ring
and the
attachment portion is a U-shaped member attached to the support plate and
having a sufficient
opening to allow the loop portion to pivot between the storage and lifting
positions. The
support plate is preferably oriented and positioned to be parallel to but
beneath the working
surface of the mat, with the attachment member located on an upper surface of
the support
plate, and the base plate is attached to a lower surface of the support plate
and is oriented
perpendicularly thereto. The lifting element is made of steel or another
metal, preferably one
that is weldable, so that the attachment member and base plate can be welded
to the support
plate. The recess is preferably a horizontally configured recess provided
beneath the working
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surface of the mat upon adjacent longitudinal beams with the base plate
extending in the space
between the beams, wherein the recess has a depth that is greater than the
combined thickness
of the support plate, attachment member and loop member so that the lifting
element resides
beneath the working surface of the mat when in the storage position.
Another embodiment of the invention relates to a crane mat having a working
surface
and comprising outer side members comprising first and second side beams or
boards of
engineered lumber, oak or other hardwoods, or bumper members of solid or
filled or unfilled
hollow plastic members that optionally may be reinforced; a core structure
comprising a
plurality of longitudinal members; a plurality of joining rods that attach the
outer side
members to the longitudinal members of the core structure; one or more lifting
elements
comprising a loop portion that is configured with an opening sufficient to
receive and allow
grasping by a hook, fingers, hand or other lifting member, and a securement
portion for
attachment to a component that is present in the core structure. The mat
includes an opening
or recess in the working surface which is configured and dimensioned to
receive the lifting
element therein in a storage position with the lifting element substantially
filling the recess
and maintained at or below the working surface of the mat when not used for
lifting or moving
of the mat or when securing articles thereto. The loop portion is movable to a
lifting position
that exposes the loop above the surface of the mat for engagement by a hook or
other grasping
element for certified overhead lifting, manipulation or movement of the mat or
for securing
other articles to the lifting element.
The core structure can includes only longitudinal members with or without
intermediate steel plates of the same height and length so that the upper
surfaces of the
longitudinal members form at least part of the working surface of the mat.
Each lifting
element then would be located in an opening that is at least partially present
in an elongated
member of the upper or lower layer and a subjacent longitudinal member or
present in
adjacent elongated and longitudinal members of the upper or lower layer, with
each lifting
element connected to a joining rod to secure the lifting element to the mat.
In particular, the
securement portion of each lifting element would include an opening sufficient
to receive a
joining member therein, with the loop and securement portions either connected
to each other
or forming a unitary lifting element, and with the joining member passing
through the
securement portion to attach the lifting element to the mat.
Alternatively, the frame member may further comprise a metal frame that
includes side
and end members, and wherein the outer side members, side members of the frame
and
longitudinal members each include a plurality of spaced lateral apertures
passing
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therethrough, with the lateral apertures being in alignment to form bores
through the mat;
wherein each joining member passes through each of the previously mentioned
members
through the aligned lateral apertures to hold the members together in the mat.
The frame
preferably includes one or a plurality of cross members attached to side
members to
strengthen the frame, with the longitudinal members located between cross
members and with
additional filler members located between the cross members and end members of
the frame,
wherein a joining member passes through the additional filler members through
aligned lateral
apertures therein to hold those members together in the mat. Thus, the one or
more lifting
elements are connected to a cross member to secure the lifting element to the
mat.
In yet another embodiment, the recess provides a sufficient opening in the mat
to
expose a portion of the joining member and the lifting element comprise a
ring, cable, or chain
that receives the exposed joining member. Advantageously, the recess opening
also provides
sufficient space to receive and maintain the lifting element in the storage
position beneath the
working surface of the mat. If desired, the opening of the recess can be
reinforced with metal
plates or a collar which protects the opening from contact by the ring, chain
or cable and
which adds stability as the mat is being lifted or moved.
The invention also provides a crane mat having a working surface and an
opening or
recess in the working surface. This crane mat comprises outer side members
comprising first
and second side beams or boards of engineered lumber, oak or other hardwoods,
or bumper
members of solid or filled or unfilled hollow plastic members that optionally
may be
reinforced; a core structure comprising a plurality of longitudinal members; a
plurality of
joining rods that attach the outer side members to the longitudinal members of
the core
structure; and one or more lifting elements. The lifting elements include a
loop portion that is
configured with an opening sufficient to receive and allow grasping by a hand,
fingers, or a
.. hook or other lifting member, a support member for supporting the loop
portion, and a
securement portion for securing the lifting element to the mat, wherein the
loop portion,
support member and securement portions are connected to each other. The mat
opening is
configured and dimensioned to have a floor for receiving the support member, a
channel for
receiving the securement portion, and a depth that allows the lifting element
to be received in
.. the opening with the loop portion in a storage position that is maintained
at or below the
working surface of the mat when not used for lifting or moving of the mat or
for securing
articles thereto, wherein the support member is secured to the floor of the
opening or recess
with the securement portion fixed in position in the mat, wherein the loop
portion is movable
to a lifting position that exposes the loop above the working surface of the
mat for
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engagement by a hook or other grasping element for certified overhead lifting,
manipulation
or movement of the mat or for securing other articles to the mat.
One version of the mat has the upper surfaces of the longitudinal members
forming at
least part of the working surface of the mat, wherein the opening or recess is
present in one or
.. adjacent longitudinal members, and wherein the mat optionally includes
metal plates of the
same height and length as the longitudinal members and which are provided
between adjacent
longitudinal members.
Another version further comprises external components including an upper layer
of
elongated members located above and attached to the core structure to protect
the core
.. structure, a lower layer of elongated members located below and attached to
the core structure
to also protect the core structure, or both of the upper and lower layers;
wherein the elongated
members are made of wood, engineered wood, metal or a thermoplastic,
thermosetting plastic,
or elastomeric material, wherein each lifting element is located in an opening
that is at least
partially present in an elongated member of the upper or lower layer and a
subjacent
longitudinal member or present in adjacent elongated and longitudinal members,
with each
lifting element connected to a joining rod to secure the lifting element to
the mat.
Another version of the mat has a lifting element that further comprises a body
member
for joining the loop and securement portions, wherein the body member extends
in the channel
and into the mat away from the support member, and is fixed in position by the
support
member and securement portion, wherein the securement portion includes an
opening
sufficient to receive a joining rod therein, and with a joining rod passing
through the
securement portion to attach the lifting element to the mat.
Also, for some mats, the core structure further comprises a metal frame that
includes
side and end members, and wherein the outer side members, side members of the
frame and
longitudinal members each include a plurality of spaced lateral apertures
passing
therethrough, with the lateral apertures being in alignment to form bores
through the mat;
wherein each joining rod passes through each of the previously mentioned
members through
the aligned lateral apertures and bores to hold the members together in the
mat.
And in yet another embodiment, an industrial mat is provided that has a
support core
that includes a frame having first and second spaced longitudinal side
members, front and rear
end members, and internal connecting or cross members, with the core
configured and
arranged to support other external components of the mat; external components
including an
upper layer located above and attached to the frame of the support core that
forms an upper
surface layer for the mat and that protects the support core, and a lower
layer located below
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and attached to the frame of the support core that forms a lower surface layer
of the mat and
that also protects the support core; and lifting elements directly attached to
the support core,
with the lifting elements comprising D-shaped members, 0-shaped members, U-
shaped
members, hooks, circular or polygonal rings, chains, or cables that are
attached to a
connecting or cross member that is attached to the longitudinal side members
of the support
core, either directly or through the upper or lower surface layers, with
sufficient strength to
provide certified overhead lifting of the mat for installation and reclamation
thereof
In a preferred embodiment, lifting element is not a chain that is attached to
a lateral rod
in an opening in the mat, nor is it a simple D- or 0-ring mounted on a plate
that is nailed or
otherwise attached to the mat. Instead, the preferred lifting elements have a
body member that
connects a movable upper portion, such as a D- or 0-ring, to the lateral rods
in a manner that
secures the lifting element to the mat in a fixed position so that only the D-
or 0-ring rotates
or is movable for exposure out of the mat opening or recess when needed for
lifting or for
securing objects to the mat. This provides unexpected advantages in the
lifting and movement
of the mat compared to an elements such as a chain or cable. It also has
better securement to
the mat compared to lifting elements such as the simple D- or 0-ring mounted
on a plate.
Thus, the preferred lifting elements provide certified overhead lifting of the
mats.
Turning now to the drawings, Figures 1 and 2 illustrate a crane mat 100 in
accordance
with a first embodiment of the present invention. For this embodiment, the
crane mat includes
side beams 110, 140 and end beams 120, 130 each made of oak or other hardwood,
and four
internal beams 125A, B, C, D each made of softwood such as pine timbers to
reduce the
overall cost of the mat. Four internal pine timbers are illustrated but the
number can vary
depending upon the size of the mat. As these pine timbers are not as abrasion
and abuse
resistance as other materials or components, they are protected on all sides
by being placed in
a frame 135.
The metal frame 135 is typically made of steel but which also can be made of
aluminum or other metals. This frame is generally rectangular and includes
flange portions on
the upper and lower sides to help maintain the internal components therein.
Generally, the
frame members are configured as a C-shaped beam with the open side of the C
facing into the
core and with the flat side facing the side beams to facilitate attachment
thereto. It is also
possible for these members to be flat plates or even I-beams. The end and side
beams can be
configured for attachment to the frame members without leaving substantial
amounts of open
space.
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The top and bottom surfaces or the pine timbers are protected one or more
different
elongated members, shown in Figures 1-2 as upper elongated boards 150A, B, C
and lower
elongated members 155A, B, C which are placed on the respective upper and
lower surfaces
of the pine timbers. The pine timbers are configured to be shorter than the
longitudinal oak
beams to provide space for the upper and lower surfaces of the pine timbers to
receive the
elongated members and form relatively flat upper and lower surfaces of the
mat. The
elongated members and more durable than the pine timbers and are typically
made of oak or
other hardwoods, plastic or elastomeric members or even metal sheets or
plates. And instead
of multiple elongated members, a single plate or sheet of steel, wood, plastic
or elastomeric
material can be used depending upon the size of the mat and the service life
performance
needed.
The mat is strengthened by the addition of steel or metal plates 105A, B, C
which are
placed between each adjacent pine timbers as well as between the oak beams and
the adjacent
pine timbers. These are needed for certain applications but they may be
considered as
optional as the present invention is also operable without these plates.
The two side beams 110, 140 which are made of white oak have dimensions of
about
12 x 12 inches and a length of approximately 16 feet. The core of the mat is
made primarily
of the frame 135 and pine timbers, the latter of which have dimensions of
approximately 12
inches wide and 8 inches high. The steel "C" beams of the frame have a height
of about 8
inches. The frame and pine timbers are located adjacent the center of the
height of the side
beams such the side beams extend approximately 1 to 2 inches above and 1 to 2
inches below
the frame and pine timbers. To prepare uniformly flat upper and lower surfaces
of the mat,
elongated boards 150A, B, C and 155 A, B, C, each of which is approximately 1
to 2 inches
thick, 8 inches wide and 16 inches long, are provided above and below the pine
timbers as
shown. The boards can be made of wood, engineered lumber, plastic or recycle
materials.
The oak beams and boards thus protect the pine timbers from abuse while
reducing the cost of
the mat due to the substitution of the pine timbers for oak timbers. And when
these elongated
boards are spaced apart, channels 152 are formed between them which allow
water to drawing
from the mat during use.
The frame is protected at the forward and rearward ends of the mat by end
beams 120,
130, but as these ends are not usually subjected to great abuse, the inclusion
of these beams
are optional. When the end beams are not used the steel frame is configured to
form the ends
of the mat. Alternatively, if desired, bumper members as disclosed in the
prior applications
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that are incorporated by reference herein can be provided on the forward and
rearward ends of
the mat to provide further protection of the ends of those pine timbers.
The side beams, pine timbers and when used the steel plates are joined
together by
joining rods 160 which extend across the width of the mat. Typically, rods 480
are carriage
bolts having a head 162 that engages an opening on one of the side beams and a
threaded end
and nut 165 on the other end of the bolt on an opening in the other side beam.
Preferably, the
ends of the longitudinal members are recessed into the mat or are provided
with a low profile
that does not protrude significantly from the mat. A number of joining rods or
bolts are used
spaced every 3 to 6 feet of length of the mat. The bolts pass through each of
the beams and
timbers and when used the plates and are secured in placed by the washer and
nut arrangement
165. The upper and lower boards 150 are either nailed or bolted to the pine
timbers.
To facilitate lifting of the mats, a lifting element 170 according to the
invention is
provided. This element is best shown in Figures 3-6. A D-shaped ring 172 is
preferably
provided that is pivotally attached to a steel support plate 174 by way of a U-
shaped channel
member 176 that is welded 178 to the steel support plate 174 to provide space
to facilitate the
pivoting movement of the ring 172. The lifting element 170 also includes a
base plate 182
that is arranged perpendicular to the support plate 174 and that is welded 184
thereto. The
base plate includes an aperture 186 that receives the support rod 160 to
secure the lifting
element to the mat. This lifting element is provided in a recess 175 that is
present in the
center board 150 and that extends onto the upper sides of the pine timbers 125
while the base
plate extends into the spacing between those pine timbers to reach the point
where the support
rod 160 passes through the pine timbers. The plate is accommodated in the pine
timbers by
the recess 175 into which the plate can be seated. To further prevent movement
of the lifting
element during use, four holes 188 are provided in the support plate to
receive nails or screws
that secure the support plate to the timbers. This provides a very secure
connection that
allows overhead lifting of the mat for installation or removal as well as to
facilitate loading or
unloading of the mats on a truck or train bed. It also prevents wear and
abrasion compared to
lifting elements that move within the mat as only the D-shaped ring needs to
be removed from
the recess to be operated.
The D-shaped ring of lifting element 170 is provided in an opening or recess
175 in the
center board 150B in such a way that when not used to lift the mat, the D-
shaped ring lies flat
in the opening so as to not hinder movement of personnel over the mat. This is
shown in
phantom in Figure 3. And while the two lifting elements are shown on the upper
surface of
the mat, it is advantageous to also provide the same arrangement on the lower
surface of the
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mat. Furthermore, the number and precise location of the lifting elements is
not critical but
can be selected by a skilled artisan depending upon the overall size and
weight of the mat.
Figure 7 illustrates a cross-section of the mat to show how the components are
joined
together. Side beams 110, 140 are joined to frame 135 and pine timbers 125A,
B, C and D.
Frame 135 is made of the preferred C-shaped members having upper and lower
flanges that
assist in confining the internal wood members in the support core. The
internal members
includes smaller boards 126A, 126B which may also be made of pine that fit
within the space
between the flanges of the frame members 135. The pine timbers on the front
and rear ends of
the mat have chamfered ends while the outermost pine timbers have a chamfered
outermost
edge in order to provide a shorter height so that they can fit into the C-
shaped members of the
frame. The remaining upper surfaces of the pine members, the upper surfaces of
the
intermediate steel plates and the flanges of the frame members for,
substantially flat upper and
lower surfaces of the support core. This facilitates attachment of the
protective elongated
members to the core structure.
The use of a small recess for the D-shaped ring also minimizes the amount of
dirt or
other debris that can enter the recess. And as the ring occupies a significant
portion of the
recess it is easy to grab the ring to move it to a lifting position.
Generally, one lifting element is located on a lateral rod at the center of
the mat nearest
one end and another lifting element is located on a lateral rod at the center
of the mat nearest
the opposite end. It is also possible to utilize four lifting elements, two
spaced lifting elements
on the lateral rod nearest the first end of the mat and two other spaced
lifting elements located
on a lateral rod nearest the opposite end of the mat. These can be provided
between the pine
timbers or between the longitudinal oak beams and pine timbers. While four
lifting elements
are sufficient in most cases, higher numbers can be used if desired. For large
mats 6, 8 or
even 12 lifting elements can be used to provide versatility in movement and
manipulation of
the mats. Preferably, the lifting elements are arranged and located
symmetrically on the
working surface or surfaces of the mat.
Figures 8-9 illustrates a variation of the crane mat of the previous
embodiment
although the same lifting element 170 is used as in Figures 1-2. Crane mat 200
has three pine
timbers 125A, B, C that have upper and lower surfaces protected by elongated
boards 250A,
B, C and 255 A, B, C. Boards 250 are the same as boards 150 in Figures 5-7 and
are smaller
in width than pine beams 220, 230. Boards 255 have the same width as pine
beams 210, 240.
While the upper and lower surfaces of the mat are formed by the upper and
lower surfaces of
the boards, this example illustrates that the width of the boards that are
used can vary as
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desired. And as previously noted, a single plate or sheet can be used instead
of multiple
boards if desired. The use of multiple boards however is preferred because if
a particular
board is damaged it can be replaced rather than having to replace an entire
unitary sheet or
plate that covers the entire top or bottom surface of the mat. In some
situations, however, a
.. plate of steel or unitary plastic or elastomeric material layer can provide
additional advantages
when covering the entire surface on the top or bottom of the mat.
As a steel frame is not used in this embodiment, the ends of the mat include
the
exposed ends of the pine timbers and steel plates. As noted, in certain
embodiments, these
ends of the mat do not need to be protected as they experience less abuse that
the sides and top
and bottom surfaces of the mats. The pine timbers and steel plates 205A, B, C
are joined
together by the rod members 260 as in Figures 1-2.
Figures 8-9 illustrate another variation of the invention. Instead of using
side beams
210, 240 that have a greater height than the pine timbers, the side beams can
have the same
height as the pine timbers. This is shown by the dotted lines on beams 210,
240. With this
.. arrangement, additional protective boards can be provided on the top and
bottom surfaces of
the side beams. This allows the protective boards to be removed from those
surfaces and
replaced so that the service life of the crane mat can be extended. The boards
would be sized
as shown above and below the dotted lines on the side beams. This arrangement
may be
useful when the side beams are made of other than wood as the upper and lower
surfaces of
the side beams can be protected by oak boards or other more rugged materials.
This
arrangement also allows pine beams to be used as side beams.
Figures 10-11 illustrate another variation of the crane mat of the previous
embodiment
with the only change being the use of smaller pine timbers in the core.
Instead of using 2 or 3
pine timbers of larger size, the crane mat 300 uses pine boards of smaller
dimensions, such as
.. 2 by 8 inches, instead of 6 by 8 or 8 by 8 inches. This results in seven
pine boards 325A, B,
C, D, E, F, G and six intermediate steel plates 305A, B, C, D, E, F. Using a
greater number of
steel plates with the reduced width of the pine boards provides a reinforced
structure that does
a much better job of withstanding loads on the mat. The steel plates are 3/8"
thick in this
embodiment but they can vary from 1/4" to 1/2" in other embodiments.
Figures 12-14 illustrates yet another variation of the invention. In these
Figures, crane
mat 400 is made only of longitudinal beams, typically of oak although other
durable materials
such as thermoplastics or thermosetting plastics (hollow or filled),
elastomers or even metal
tubes can be used. The same lifting element 170 is used as in the preceding
Figures. In
Figures 12-14, mat 400 has four longitudinal beams 410, 420, 430, 440. Unlike
the other
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embodiments, there are no intermediate steel plates, no protective members nor
is there a
metal frame. The beams are joined in the same manner as in the other figures
by rod members
or carriage bolts that pass through apertures that extend through the width of
the beams.
In the preceding Figures, the bottom surface of the mat is not shown, but 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.
Figure 13 illustrates the crane mat 400 with longitudinal beam 430 removed so
that the
position and placement of the lifting element can be shown. The lower vertical
plate of the
lifting element 182 is placed in a vertical recess 177 between beams 420 and
430. Support
plate 174 is located in recess 175 and is secured to the mat by engaging rod
member 460
which passes through aperture 186 as well as be being nailed or screwed to the
beams though
the apertures on the support plate 174.
The mat is provided with at least two lifting elements each located in an
opening
between the innermost beams when an even number of beams are use or between
the
innermost bean and an adjacent beam when an odd number of beams are used.
Alternatively,
for wider mats, two spaced lifting elements can be provided at each end of the
mat.
Figures 13-14 illustrate the lifting element 170 in use. The hook 450 which is
connected to a high strength chain of a lifting device engages D-shaped ring
172. The same
type of attachment is made to the lifting element on the other end of the mat.
As the mat is
lifted, the chain and hooks provide an angle of 60 with respect to the mat
surface, with an
imaginary line passing from the chain though the lifting element and through
the center of the
rod member that is located in hole 186. This provides the optimum arrangement
for safe
lifting of the mat by the lifting device. Using the same length of chain with
each hook assures
that the 60 angle is achieved.
It is also possible to configure the opening sidewall to support the D ring in
an upright,
generally upright or angled position to allow attachment of a hook to the ring
without
requiring separate holding of the ring by an operator or worker. This is
advantageous in that
the worker has two hands in which to attach the hook rather than using one
hand to hold the
ring in position while using the other hand to attach the hook. There are a
number of ways to
facilitate this maintenance of position. The D ring can lie against the
opening and be
generally upright or at least at an angle of about 45 degrees or greater and
typically at 60 for
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optimum lifting performance. The U-shaped part that attaches the D ring to the
support plate
can also be configured with a structure thereon that assists in maintaining
the ring at the
desired angle for engagement by a hook or other lifting member. The structure
can be a bump
or protrusion on the U-shaped part that does not allow the ring to move past a
certain angle.
For example, the ring can be prevented from moving more than 120 from the
storage
position as this provides the 600 lifting angle. The angle has to be greater
than 90 so that the
weight of the ring maintains it in an upright or substantially upright
position.
Figures 15-16 illustrate another embodiment of the invention. This crane mat
500 is
similar to that of Figures 1-2 such that the same components have the same
element numbers.
Instead of having an open frame, however, the frame 560 of Figures 15-16
includes cross
members 585A, 585B. These cross members are placed near the front and rear
ends of the
mat and are bolted to the side members of frame 560. In fact, all frame
members can be
bolted together to facilitate construction of the mat.
Lifting elements 570 A, B are provided and are configured in a similar manner
to
lifting element 170 of Figures 1-2, with the exception of the omission of base
plate 182.
Instead, support plate 174 is welded to an upper surface of each cross member
so that it is
securely attached to the mat. As above, the D ring 172 of the lifting element
resides in a notch
or recess 175 that is present in protective board 150B. As in the other
embodiments, this
allows the upper surface of D-ring to be flush with or slightly below the
surface of the mat
while blocking the recess 175 so that workers will not step into the hole or
trip over the D ring
when it is not in use. The lifting element 570 also allows the mat to have to
have certified
overhead lifting capabilities.
The pine beams 125A, B, C, D in this embodiment are shorter than in the
previous
embodiment and extend between the cross members 585A, 585B. The same is true
of steel
plates 105A, B, C. The space between the cross members in the end plates of
the frame can
be left open if desired, but in a preferred embodiment are filled with boards
and plates in the
same arrangement as between the cross members. In the front end of the frame,
shorter pine
timbers 126A, B, C, D and steel plates 106A, B, C are used to mimic what is
present in the
middle of the core structure between the cross members. These shorter pine
timbers and steel
plates are also connected to the mat through the lateral rod 160 that passes
through the space
between the cross members and frame end members. Similarly, on the opposite
end of the
frame, shorter pine timbers 127A, B, C, D and steel plates 107A, B, C are used
to mimic what
is present in the front end of the frame. These shorter pine timbers and steel
plates are also
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connected to the mat through the lateral rod 160 that passes through the space
between the
cross members and frame end members.
Figure 16 is an exploded view of frame 560 of Figure 16. To assemble the
frame, one
longitudinal member 562 and one end of the end members 563, 565 and cross
members 585A,
B can be welded to the longitudinal member 562. The other longitudinal member
and cross
members 585A, 585B include side plates 585C, 585D, respectively. These plates
are provided
with holes 566A, 566B that align with holes on the side members of the frame
so that the
cross members can be attached to the frame using bolting. This is typically
done after the
internal beams and if used steel plates are provided in the frame between the
cross members
and between the cross members and frame ends, otherwise it would be difficult
to insert those
internal components into the frame, especially when inwardly directed "C"
shaped steel
members are used to make the frame. The use of bolting allows the frame and
cross members
to include upper and lower flanges which assist in maintaining the pine beams
and steel plates
in the core structure of the mat. If flange members are not provided on the
frame and cross
members, then the entire frame including the cross members can be welded
together prior to
the addition of the internal components which are then slid into the frame.
And as in the other embodiments, the materials for the various components of
crane
mat 500 can be made of any of the different materials specified herein. Also
various
combinations of materials can be used for any particular sized mat for any
intended use
thereof. And the elongated boards that are used to protect the core structure
can be provided
as separate boards or as a single plate or sheet. Multiple plates or sheets
can be used for larger
size mats. As noted, the material for these sheets or plates can be wood, a
metal, preferably
steel, a thermoplastic, a thermosetting plastic or an elastomer. When a steel
plate is used the
lifting element can be welded onto the steel plate or an opening can be
provided in the steel
plate so that the lifting element is attached as shown in the preceding
embodiments.
Figures 17, 18A, 18B, 19A and 19B illustrate different lifting elements for
use in any
of the crane mats disclosed herein. Each of these lifting elements 600 is in
the configuration
of an eyelet. The lifting element 600 has a body 605 with a first end thereof
610 having a
securement portion in the form of an opening 615 for receiving and connecting
to a lateral rod
and a second end 620 having a loop portion 625 that acts as grasping means for
a hook or
connecting element of lifting equipment to engage the loop portion for lifting
and
manipulation of the mat. The loop portion 625 is an aperture in the second end
620. Instead
of an aperture, the loop portion can be a hook element or J- or L- shaped bar
that can engage a
mating connecting element on the lifting equipment.
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The body 605 is typically a flat plate that preferably has rounded edges but
it also can
be a bent or angled member that near one end has the necessary aperture to
receive the lateral
rod therein for attachment to the mat, and on the opposite end includes the
aperture or other
loop portion. In some cases, a chain or cable can be used instead of the flat
plate with the
chain or cable passing around the rod and out of the aperture to be engaged by
the lifting
equipment. The flat plate is preferred because it is compact and requires a
smaller hole than a
chain or cable.
A vertical recess 650 having a flat bottom surface 655 is configured and
dimensioned
to hold and maintain the lifting element 600 therein in a first retracted or
storage position as
shown in Figure 18B when not in use and to allow retrieval and removal of the
second end
620 of the lifting element from the opening or recess 650 to a second
operative position that
exposes the loop portion 625 to allow grasping when the mat is to be lifted or
manipulated, as
shown in Figure 18A. The opening 650 is either positioned at an end of the mat
so that it is
open at that end as shown or has a sufficient volume to allow a user to reach
therein to grab
and move the loop portion 625 from the retracted position to the operative
position. And
while Figure 18B shows the lifting element well below the surface of the mat,
in practice, the
open space above the lifting element should be minimized so that the lifting
element helps
form part of the surface of the mat. This prevents tripping or stumbling by
workers who step
into the opening 650 when moving across the mat surface.
The lifting element 600 shown in Figures 17 and 18A, 18B is spaced from the
end of
the mat by a few feet, e.g., 1 to 3 feet. To provide access to the lifting
element, the opening in
which the element resides is elongated so that it extends from the point where
the lifting
element is present all the way to the end of the mat. This provides access to
the lifting
element to remove it from its retracted position, which is shown in Figure
18B, to an operative
position as shown in Figure 18A. Again, the lifting element 600 has an arcuate
first end to
allow the lifting element to more easily pivot about the joining rod between
those positions.
And although the opening 650 is illustrated as being much longer than the
length of the
lifting element, it is also possible to simply widen the opening about the
retracted lifting
element rather than have a thinner opening that extends to the end of the mat.
The
configuration of the openings 650 should simply be sufficient to allow an
operator to be able
to reach in and grab the lifting element to raise it to its operative
position. When the opening
is placed further back in the mat, it is generally widened to allow the hand
of the operator to
reach into the opening.
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Figures 19A and 19B illustrate a variation of the lifting element of Figures
17, 18A
and 18B. The lifting element features are the same as in the prior Figures,
but the vertical
recess 660 is configured with a sloped bottom wall 665. This enables the
recess to be of
overall smaller size while still retaining lifting element 600 below the
working surface of the
.. mat. Also, the recess 660 does not need to extend to the end of the mat and
terminates at a
vertical wall 670.
A number of variations of the lifting element of the preceding Figures can
also be used
in the present invention. Instead of two holes separated in the plate as shown
for lifting
element 600, a single, larger hole can be provided in the plate. The open
center plate can be
.. used on smaller sized mats where the overall lifting element does not need
to be as long as
lifting element 600. It is possible to obtain a metal or steel stamping in the
desired shape and
thickness which will have the same outer circumference and size of lifting
element 600 but
without the body portion 605 between the two openings ¨ in effect being a
single larger
opening.
And for certain mats, it is possible to instead use a ring that is made of a
metal,
preferably steel, bar of cylindrical or rectangular cross-section that is
configured in the shape
of a ring with the ends of the bar welded together. This ring can be shaped as
shown in the
prior Figures with a similar outline to the shape of those lifting elements,
or it can be made as
an oblong, oval, elliptical or circular ring. These non-linear shapes are
preferred as they are
easy to manipulate with respect to removing a portion of the ring from the
slot for use when
the mat is to be moved, as well as to allow the ring to fall back into the
slot into the storage
position after the mat is installed and in use. A shape other than circular is
preferred,
however, as it will more easily fit within the vertical recess 650 or 660. The
shape of the ring
would be selected based on the thickness and overall weight of the mat. This
will also be used
.. to determine a suitable thickness for the plate embodiment of the prior
Figures or for the
diameter or circumference of the cylindrical or rectangular rod that is shaped
as a ring.
To avoid the lifting element damaging the wood sides of the slot or recess,
the edges of
a rectangular bar or plate can be rounded. Alternatively, the slot or recess
can be lined with a
plate preferably of metal in areas where contact by the lifting element during
movement of the
.. mat is expected. Such a construction requires additional time and labor to
configure the slot
or recess so that the collar embodiment is preferred. A metal collar that can
be used to protect
the opening in the mat from damage due to contact with the lifting element is
described as
element 1302 in US patent application Ser. No. 15/244,614 in Figures 6 and 7.
This collar
protects against contact and abrasion from the lifting element when lifting
the mat.
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Alternatively, other replaceable structure of metal or other materials can be
used to protect the
sides of the opening.
For any of the embodiments that are used with the slot of the preceding
Figures, the
angle of the sloped bottom wall is sufficient to allow the lifting element to
fall back down
under its own weight into a position where it does not protrude above the
working surface of
the mat. And when the lifting element is to be used for receiving a hook of a
crane or other
heavy equipment device, a worker can simply reach into the slot and pull up
the lifting
element to expose an opening or hole that the hook can engage to then move the
mat.
Figures 20-23 illustrate another lifting element 700 in the form of a T shaped
member
that is similar to that of Figures 3-6. Figure 20 illustrates that the D ring
705 is attached to a
widened, reinforced opening 710 on one end of the lifting element 700. This
reinforced
opening acts as a support plate for the D ring and is configured as in the
other embodiments so
that the D ring 705 can form a 60 angle with opening 720 when a lifting hook
755 is attached
to the D ring 705. As noted herein, this angle has been found to provide ideal
overhead lifting
capacities. Using hooks 755 connected to each lifting element from lines that
are joined at a
common point achieves this arrangement, but if necessary the reinforced
opening 710 can
include bumps or other protruding structures on the sides so that the D-ring
will stand in
position to form the 60 angle.
The lifting element 700 is provided in a rectangular recess 750. When the D
ring 705
of the lifting element 700 is needed for use, it is raised for attachment of a
hook or other
lifting member thereto. For this, the D-Ring is removed from the recess 750 so
that it can be
located above the working surface of the mat as shown in Figure 23 to allow
attachment of the
hook 755 to the D-ring. And when the D ring 705 is not being used for lifting
the mat or for
tying other articles to the mat, it can conveniently retracted into the recess
750 or opening in a
storage position wherein the D ring substantially fills in the recess or
opening. In this
position, a worker or other person operating on the mat has less of a chance
of stepping into
the opening or recess as it is more or less filled with the lifting element.
This can prevent
injuries to workers moving on the mat. Also, the storage of the lifting
element beneath the
mat surface clearly avoids workers tripping over an exposed lifting element
when moving
about the mat.
It is also advantageous for configuring the recess in the mat to have a depth
that is only
slightly larger than the ring member of the lifting element, e.g., but no more
than 0.25 to 0.5
inches. This minimizes the open area of the recess and facilitates cleaning of
the recess by
removal of dirt or other foreign objects that enter the recess. This minimized
area of the
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recess provides another advantage by presenting a smaller opening that is less
likely to be
causing tripping or stumbling of workers operating on the surface of the mat.
Figures 24-25 illustrate yet another lifting element 800 in the form of an "I"
shaped
member. This lifting element includes a specially shaped ring member 805 is
securely
attached to an enlarged head member 810. Typically the ring member 805 is
attached to the
head member 810 by a pin that passes through the head member 810. For lighter
weight mats,
the ring member can be configured with end legs that securely engage openings
in the head
member 810. For either embodiment, the ring member can pivot back and forth so
that when
not in use it can lay flat against a supporting surface such as the floor of a
recess or opening in
the mat. As in the other embodiments described herein, the ring member 805 and
head
member 810 would be located in a recess in the mat so that when not in use the
head member
810 and ring member 805 would substantially fill in the opening. And when
needed to move
the mat, the ring member 805 can simply be pivoted out of the recess and above
the mat
surface for engagement.
The lifting element 800 has a body member 815 that passes through the entire
beam of
the mat construction. The opposite end of the lifting element 820 is threaded
so that it can
receive a nut 825 and washer 830 to secure the lifting element to the mat. The
nut and
threaded end of the body member are located in a recess on the opposite side
of the mat so that
they do not extend out of the surface on that side of the mat.
For additional securement, round, square or rectangular plates 835, 840 can be
provided in contact with the beams to provide greater resistance against
lifting element pull-
out when the mat is being moved. These lifting elements 800 can be used alone
or in
combination with the other lifting elements disclosed herein depending upon
the type of mat
being made and the need for having such lifting elements for moving the mat or
for tying
articles to the mat.
Although Figures 24 and 25 do not show the lifting element seated in an
opening or
recess, it would be understood that this would be necessary for the same
reasons previously
mentioned and with the same configurations so that the ring element does not
protrude above
the working surface of the mat. Ring element 805 can be pivoted downward,
i.e., to the right
or left in Figure 25, in order to be maintained in the recess. Therefore, the
recess will have a
height that is at least as high as head member 810, and a width that would be
at least as wide
as the length of ring member 805 and half the width of head member 810.
Also, plate 835 can be of a width and length that encompasses the entire floor
of the
opening or recess. Of course, a plate having dimensions that are smaller than
the recess is also
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acceptable. The same is true for plate 840. The goal of plates 835 and 840 are
to help
distribute the load on the lifting element to the surface of the member to
which it is attached as
well as to more securely connect the lifting element to the mat.
And to the extent that the plates 835, 840 have smaller dimensions than the
recess, it is
also possible to provide a further recess or cutout below the plate so that
the plate has an
exposed surface that is at the same level as the floor of the lifting element
recess. This will
also further limit the depth of the lifting element recess needed to maintain
the lifting element
below the working surface of the mat.
Washer 830 is not always needed but is typically used to facilitate the
attachment of
the lifting element to the member of the mat. This is typically round but can
be square or of
other peripheral shapes. If desired, the washer can be a lock washer to offset
loosening of the
nut from the threaded rod.
And to the extent that the mat has upper and lower working surfaces that
enable either
one to be selected as the top of the mat when installed, the lifting elements
can be provided on
the opposite side of the mat with a reverse orientation to the ones shown in
Figures 24 and 25.
This of course would apply to any of the arrangements of lifting elements
disclosed in the
present application. It is often common for such mats to include both upper
and lower
working surfaces so that upon installation, the surface in better condition
can be selected as
the top or exposed surface of the mat that is used to experience worker or
equipment travel or
placement thereon.
The crane mats of the invention may be 2' wide to 12' wide with all mat
components
being square or rectangular timbers or beams/bumper members connected together
by the
lateral rods. Various mat thicknesses can be used from 2" to 24". And instead
of single
beams, boards or layers of boards can be used. In a preferred embodiment, oak
or other
hardwood beams can be used alone at those dimensions with the beams connected
by the
lateral rods although combinations of different materials can be used if
desired. For any of
these embodiments, at least two lifting elements are provided on the upper
working surface
with the base plate of each lifting element connected to one of the lateral
rods. The lifting
element would preferably be one like lifting elements 475 or 476 and be
provided in a recess
in one or more of the mat components. Intermediate steel plates can also be
included between
the beams if desired.
Figures 26-29 illustrate another crane mat 900 in accordance with the present
invention. For this embodiment, the crane that includes internal beams made of
softwood
such as pine timbers to reduce the overall cost of the mat. As these timbers
are not as abrasion
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and abuse resistance as other materials or components, they are protected on
all sides by one
or more different mat components. In the simplest construction, the adjacent
pine timbers can
be assembled into the core of the mat and protected on either longitudinal
side with oak
beams. The pine timbers would also be configured to be shorter than the
longitudinal oak
beams with the upper and lower surfaces of the pine timbers protected by more
durable
elongated members. In a further embodiment, a steel or metal plate can be
placed between
each adjacent pine timbers as well as between the oak beams and the adjacent
pine timbers to
further strengthen the mat.
All mat components and their arrangement in the mat are best illustrated in
Figure 27.
This crane mat 900 includes two side beams 910, 920 which are made of white
oak and which
have dimensions of about 12 x 12 inches and a length of approximately 16 feet.
The core of
the mat is made primarily of three pine timbers, each labeled 930, which have
dimensions of
approximately 12 inches wide and 8 inches high. The pine timbers are located
adjacent the
center of the height of the side beams such the side beams extend
approximately 1 to 2 inches
above and 1 to 2 inches below the pine timbers. To prepare uniformly flat
upper and lower
surfaces of the mat, boards 940, each of which is approximately 2 inches
thick, 8 inches wide
and 16 inches long, are provided above and below the pine timbers as shown.
The boards can
be made of wood (and specifically including the eucalyptus grandis species),
engineered
lumber, plastic or recycle materials. The oak beams and boards thus protect
the pine timbers
from abuse while reducing the cost of the mat due to the substitution of the
pine timbers for
oak timbers. And when these boards are spaced apart, channels 955 are formed
between them
which allow water to drawing from the mat during use.
And although the timbers are exposed at the forward in rearward ends of the
mat, these
are not usually subjected to great abuse. Additionally, if desired, bumper
members can be
provided on the forward and rearward word ends of the mat to provide further
protection.
Another embodiment of the invention that is shown in Figure 29 is the use of
rectangular steel plates 950 that are approximately 3/8 of an inch thick and
have dimensions of
12 inches high and 16 feet long. Four plates are shown, one between each beam
and timber,
to provide additional strength to the mat. While these plates are shown as
being the same
height as the side beams, alternative embodiments utilize plates that are 1 to
2 inches shorter
than the side beams of the mat. When such shorter plates are used, the upper
and lower
surfaces of the mat are thus provided with channels that allow water to drain
from the mat
during use. The plates can be of the same height and length as the pine
timbers, or they can be
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1 to 2 inches shorter than those timbers. The shorter steel plates reduce the
overall weight of
the mat compared to larger steel plates while still providing additional
ruggedness to the mat.
The side beams, pine timbers and plates are joined together by bolting 960
which
extends across the width of the mat. A number of bolts are used spaced every 3
to 6 feet of
length of the mat. The bolts pass through each of the beams, plates and
timbers and are
secured in placed by a washer and nut arrangement 965. The upper and lower
boards 940 are
either nailed or bolted to the pine timbers.
To facilitate lifting of the mats, a new lifting element arrangement is
provided. This
arrangement includes a D-shaped ring 970 that is pivotally attached to a steel
plate 975 that is
welded to the steel plates 950 that are present on the outer sides of the pine
timbers 930 and as
well as in between the pine timbers. The plate is accommodated in the pine
timbers by a
formed slot 980 into which the plate can be seated. Also, the lifting element
plate 975 would
be welded at its ends to two or three of the longitudinal reinforcement plates
950 to provide a
very secure connection that will would allow overhead lifting of the mat for
installation or
removal as well as to facilitate loading or unloading of the mats on a truck
or train bed. And
the D-shaped ring is provided in an opening 985 in the center board in such a
way that when
not used to lift the mat, the D-shaped ring lies flat in the opening so as to
not hinder
movement of personnel over the mat. And while the two lifting elements are
shown on the
upper surface of the mat, it is desirable to also provide the same arrangement
on the lower
surface of the mat. Furthermore, the number and precise location of the
lifting elements is not
critical but can be selected by a skilled artisan depending upon the overall
size and weight of
the mat.
Figures 30 and 31 illustrate another 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, 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
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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 32, includes first and second longitudinal
members (1120,
1125) that are joined together by a plurality of cross members 1130.
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 31 and 32, 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
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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.
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. When filler
is to be added to
the frame, the frame can be partially welded while leaving the last side or
end unwelded so
that it can be attached by bolting after the internal components are added.
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.
As in other embodiments, 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
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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 31 shows
the rods 1160 passing through side beam 1105 and toward the side structure:
Figure 32 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 32 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 30.
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
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,
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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.
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 ends of the
mat.
Figure 30 also illustrates a lifting element 1190 in the form of a chain the
ends of
which are secured to a joining rod 1160. Each end of the chain 1190 passes
through an
opening 1185. The chain is configured of steel having sufficient strength to
be able to lift the
entire mat without bending or breaking. Also, the links at either end of the
chain can be
securely attached to the joining rod when the mat is assembled.
In a preferred arrangement, only one end of the chain 1190 is permanently
secured to
the joining rod, while the other is attached by a conventional connectable
link. Thus, after the
ma is moved into position, the chain can be disconnected and stored inside
support structure
so that personnel working on the mat will not trip over the chain.
Alternatively, if a removable chain is desired, such as may be supplied with
the
equipment used to move the mats, the chain can be provided with a connectable
link on each
end so that the workers can attach each end of the chain to the joining rod
when the mat is to
be moved. After the mat is installed, however, the chain can be removed from
the joining rod
and reused for moving or installing other mats. This again provides greater
safety for workers
as the chains are not present on the surface of the mat during use.
And for additional safety, the size of the opening 1185 is reduced compared to
mats of
the prior art. As the opening 1185 provided for connecting the chain is much
smaller than the
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previous opening or cut away beam that exposed the joining rod, personnel who
are working
or conducting operations upon the mat have a much lower chance of stepping
into hole 1185.
Figure 31 illustrates that the joining rod 1160 includes a flange or ring 1195
which is
welded to the joining rod beneath hole 1185. This flange or ring 1195 is used
to retain the end
or connecting link of the chain 1190 in the proper position beneath hole 1185.
In this way, the
chain is pulled upward in a way that does not interfere with elongated members
1145A,
1145B.
As noted in Figures 30-32, openings 1185 are provided on the near the front
and rear
portions of the upper surface of the mat, as well as on the lower front and
rear portions. This
allows the installer to grasp any side or end of the mat to facilitate
installation. And when a
removable chain is provided, it can simply be attached to the holes at the
easiest accessible
end of the mat for lifting.
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 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.
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 of
the
materials disclosed herein.
As these mats are relatively massive, provisions should be made for moving,
transporting and installing the mat at the desired field location. For this
purpose, holes or
recesses are provided in the upper surface, lower surface, or both to provide
access to the
lifting elements or 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.
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Turning now to Figures 33 and 34, 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 33 and 34 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.
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
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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 34 where the relative positions of the joining rods 1260A, 1260B are
illustrated, along
.. with sleeves 1265A, 1265B.
Figures 33 and 34 illustrate a lifting element in the form of a lifting chain
1190 for a
stepped mat 1200 which is used to provide an interlocking configuration with
adjacent mats.
The connection of chain 1190 to the joining rod is the same as shown in
Figures 30-33, with
the exception that the joining member 1160A on the top portion of the mat
would be used
when the chain or hook is accessing the mat from the top surface, while
joining member
1160B would be used when the chain or hook is accessing the mat from the for
the bottom
surface. As in the other figures, the joining rod would include a flange or
ring element 1195
to assist in positioning the terminal chain links in the proper location on
the joining rod for
lifting of the mats.
Figures 35 and 36 illustrate a metal collar 1302 that can be used to protect
opening
1185. As shown, the collar 1302 has a flat upper plate 1304 that protects the
surface of
elongated members 1145A and 1145B adjacent opening 1185. Collar 1302 also
includes a
side plate 1306 which closes the side of opening 1185 and also protects the
inner cut edges of
opening 1185 in elongated members 1145A and 1145B. In particular, the inner
cut edges of
.. opening 1185 are protected by an inwardly extending wall 1308 which is bent
from the top
plate 1304 of collar 1302. This wall 1308 protects against contact and
abrasion from the chain
when lifting the mat. The collar member may also be designed to be in contact
with the lifting
member (1332 or 1328) to add stability to the assembly when the mat is being
hoisted or
moved. In addition to being used with a chain that can be attached to the mat
through the two
openings, the collar also facilitates attachment of a hook or other elongated
member from a
crane or other heavy equipment vehicle to engage joining rod 1160 for lifting
or installation of
the mat.
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Figures 37-39 illustrate additional lifting elements for the mats of the
invention. These
are shown schematically in Figure 37 side by side although in practice these
elements would
most likely be used separately or at least in different areas on the mat.
One preferred element is a D Clip 1322, having a D-shaped ring 1323 the ends
of
which engage a metal tube 1324 that is welded to the top plate 1133 of one of
the crossing
members 1130. This structure allows the clip 1322 to be rotated to the
position where it is
perpendicular to the crossing member top plate 1133 so that it can be engaged
by a hook of a
crane or other heavy equipment vehicle. After the mat has been placed for
service, and the
hook removed, the clip 1322 can rotate so that it lays flat against the angled
side wall 1345 of
the opening in the elongated member, as shown in Figure 38. This opening does
not have to
be deep and simply allows the clip 1322 to be pivoted through an angle of
between 90 and
180 to facilitate access to and movement of the clip as the mat is being
lifted. As in the other
designs, the D clip can be provided in multiple locations on the mat, such as
near the forward
and/or rear ends or both on either or both of the upper and lower surfaces of
the mat so that
the mat can be lifted no matter how it is located on a transporting truck or
train or after being
installed. If desired, depending upon the width of the mat, a plurality of
these lifting elements
can be provided. They generally are provided about 10 to 24 inches away from
the front or
back end of the mat and preferably on the top and bottom surfaces. Typically,
one or two
clips near each end of the mat are all that would be necessary for
manipulation of the sizes of
the mats of the present invention, but a skilled artisan can determine whether
more or less
lifting elements are needed for any particular mat size and design.
Figures 37-39 also illustrate an alternative embodiment of a U-shaped member
1332
that is attached to the support structure in a way that the U-shaped ring 1335
does not protrude
above the elongated members on either the top or bottom surfaces of the mat.
The hook 1332
is welded to a plate 1334 that is mounted on a rod 1336 that passes through
the support
structure. While only one U-shaped member is often suitable for lifting the
mat from one
side, it is advantageous to provide the opposite end of the rod with a second
U-shaped member
1328 of the same configuration protruding from the lower surface of the mat as
this allows the
mat to be lifted from either the top or bottom surface. In a non-operative
state, as shown in
Figure 38, each U-shaped member sits in an opening in the elongated member
that has angled
sides 1345 with its upper member approximately uniform with the top surface or
bottom
surface of the elongated members of the mat. The angled holes 1345 are
essentially the same
regardless of whether clip 1322 or U-shaped member 1332 are used and allow
greater access
to the lifting member.
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Rod 1336 is mounted for reciprocal motion through a bushing 1342 that is
located in a
plate 1344 that is welded to a central portion of the support structure,
typically to one of the
cross members. Rod 1336 is also capable of rotating in bushing 1342 as well as
in the
bushings that re provided in the upper and lower portions of the support
structure so that U-
shaped portions 1322, 1328 can rotate 360 degrees to facilitate attachment of
a crane hook or
manipulation of the mat during lifting or movement. Plate 1344 is preferably
attached to cross
members or side beams of the support structure. Bushings 1347, 1349 are
provided in the
upper and lower plates of the cross members or side members of the support
core. The U-
shaped portions 1322, 1328 are each maintained in a static position by springs
1346, 1348.
When the mat is to be lifted, the ring 1335 is engaged with another hook from
a crane or
heavy equipment vehicle and as it lifts the mat, spring 1348 is compressed
with ring 1335
being pulled partially out of the angled hole. This arrangement allows the
hook on either U-
shaped member on either side of the mat to be accessed and pulled for lifting
the mat. After
the lifting operation or placement operation is complete, and the hook is
removed, the U-
shaped member would return back to its normal unhooked position.
As above with the D-shaped lifting element, each U-shaped member is provided
in an
opening 1345 which is beveled or otherwise angled or widened to allow access
to the U-
shaped member by the crane hook.
For certain mats, the U-shaped member can be simply welded to a plate on the
top of
the of one of the cross members, but in this embodiment the U-shaped member
must extend
sufficiently above the top surface or bottom surface of the mat to allow
access by a crane
hook. For this reason the spring mounted lifting elements are preferred.
Figures 40 and 41 illustrate another embodiment in the form of a
crane/pipeline mat
1700 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 1700 includes two side
beams 1705, 1710,
a steel box frame 1720, an upper layer of elongated members 1715A, 1715B,
1715C, and a
lower layer of elongated members 1725A, 1725B, 1725C. The core structure can
be between
2 and 3 feet wide depending upon the width of the side beams. The upper or
lower layers can
also be a single sheet or plate of wood or metal of various thicknesses
depending upon the size
of the mat and the supporting properties that are needed for the intended. As
noted herein,
multiple plates or sheets can also be used if desired.
The steel frame 1720 includes a forward lifting element 1735 and two upper
side
lifting elements 1740. 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
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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 as described herein. The lifting elements
can be
used with any of the mats disclosed herein provided that the appropriate core
structure is
present.
The components of mat 1700 are more clearly shown in the exploded drawing of
.. Figure 40. The steel frame 1720 is shown as having a plurality of
components including two
elongated side components, a front end component, a back end component and two
cross
members 1745, all of which are welded or bolted together to form the frame
1720. Side beam
bolting members 1735 are also welded to the box frame 1720. These bolting
members are
configured to pass through openings in the side beams 1705, 1710 to secure the
side beams to
the steel box frame 1720. This is done by tightening nuts onto the ends of the
bolting
members 1735 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 1730, 1740 are preferably in the shape of a D ring which
is
welded or bolted to the box frame 1720 or its cross members 1745 as best shown
in Figure 41.
The upper layer elongated members 1715A, 1715B, 1715C, and lower layer
elongated
members 1725A, 1725B, 1725C are also bolted to the box frame 1720.
As the box frame 1720 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 1750 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.
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Additionally, the mats can be made of various combinations of components
including
frames of a metal such as steel or of a thermosetting plastic. The internal
components in the
frame can be beams, board or other structural shapes of wood, engineered wood,
plastic or
elastomeric materials. These can be of sizes that vary from width and height
dimensions of
about 2" by 2" to as much as 24" by 24". The interior timbers can be from 2" x
2" up to 12" x
12" or even 16" by 16". Generally, the various beams and mat components are
square but
rectangular shapes are also acceptable. Useful core thicknesses are 2", 3",
6", 8", 12" and 16"
with the upper and lower protective boards making up the balance of the
thickness of the mat.
The upper and lower protective boards can also be provided in multiple layers
rather than in
larger thicknesses, and these are attached to the mat by the use of various
fasteners that are
generally known and used in the art. Bolting is preferred, however, as that
allows any
damaged beams or boards to be removed and replaced while the core of the mat
is reused.
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. In particular, it would be understood that the
various sizes,
materials, configurations and arrangements disclosed herein may be combined
and constructed
in any way that is feasible to create a hybrid may for any particular end use.
Accordingly, all
suitable modifications and equivalents may be resorted to falling within the
scope of the
appended claims.
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