Note: Descriptions are shown in the official language in which they were submitted.
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ACCESS FLOOR SUPPORT STRUCTURE
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority of United States Provisional Patent
Application
Serial No. 60/880,096 filed January 12, 2007.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO MICROFISHE APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to access floor systems, and more particularly to
access
floor systems that use inexpensive, sub-floor support structures made of
recycled plastics that are
flame retardant and have a desired amount of elasticity and impact strength.
Description of the Related Art
Office buildings with access floor systems, such as the access floor system
disclosed in U.S. Patent No. 4,905,437, are very popular. Some important
reasons for their
popularity is that they can be easy to install, easily adaptable for different
power and
communication network configurations, and can be easily modified after
installation if the
tenant's needs change.
Access floor systems, such as the one disclosed in the '437 patent, include a
plurality of interconnected support structures, called support modules that
are laid out in a side-
by-side manner to form a grid matrix over the floor's concrete slab as shown
in FIG. 1. Each
support module is of unitary construction and includes a central prop and
three triangularly
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aligned side props. The central prop and side props are arranged in a square
grid arrangement.
Each side prop includes a hollow cylindrical body portion with a center boss.
Located laterally from the central prop on the side opposite the side props
are
three triangularly aligned prop pads. The prop pads are arranged in a square
grid arrangement
with the central prop and identical to the square grid arrangement made by the
side props and the
central prop. Each pad includes four upward extending clips designed to engage
the center boss
located on the side props on an adjacent support module. Each pad and the
central prop includes
holes that enable them to be securely attached to a concrete slab using
suitable connectors.
Extending between the center prop and the side props and the pads are
extension
arms. The arms are semi-circular in cross-section with a flat bottom surface
that are even or
flush with the central prop, the side props and the pads thereby enabling the
entire support
module to rest evenly over the concrete slab.
In order to keep the costs of materials and installation as low as possible,
the
support modules used in access floor systems are typically made of
polypropylene that can be
injection molded. Recently, new building codes have been promulgated in many
municipalities
that require the support members used in access floor systems be made of flame
retardant.
Unfortunately, adding a flame retardant chemical to the polypropylene changes
the support
module's elastic and impact strength properties.
Also, many municipalities have promulgated rules that require the entire
access
floor system installed on a floor or space in a building be removed if it is
no longer being used.
With these new rules, it is anticipated that large quantities of recyclable
plastics used to make
support modules will soon be available and that the demand for support modules
in an access
floor system made of recyclable material will increase.
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What is needed is an improved support module designed for an access floor
system that has good flame retardant properties, made of recyclable
polypropylene, and has the
desired elastic and impact properties necessary for an access floor system.
SUMMARY OF THE INVENTION
The above stated objects are met by the improved support structure for an
access
floor system disclosed herein made of recyclable polypropylene with a
reinforcing filler and a
fire retardant added thereto to produce a module with suitable impact strength
with sufficient
elastic and flame retardant properties. In the preferred embodiment, each
module is made of
recyclable polypropylene with a modulus of elasticity to approximately 87,000
MPa and an
impact strength of approximately 7.5 ft.lb./in. To produce such a support
module with a
modulus of elasticity of approximately 130,000 MPa and a minimum impact
strength of 1.9
ft.lb/in, a reinforcing inorganic mineral filler, approximately 5% by weight,
such as talc or
montmorillonite clay is added to the recycled polypropylene resin. This is
contrary to the
teaching in the prior art of compounding plastic material where it is
generally believed that
adding a mineral filler to polypropylene resin increases strength and
stiffness, but reduces impact
strength. Tests have shown that not only is the modules impacts strength and
modulus of
elasticity increased, but also one particular filler, montmorillonite clay,
has fire retardant
properties as well.
Also disclosed herein is the use of an optional binding additive to the
polypropylene and filler composition to improve the bonds between the
polypropylene polymers
and the filler.
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DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a floor support module found in the prior art.
FIG. 2 is a table showing the ingredients used to make the concentrations used
in
the experiments shown in Table 3.
FIG. 3 is a table showing the experimental test results of a polypropylene
polymer, the mineral inorganic filler and use of the optional binding
additive.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An improved support module for an access floor system disclosed herein made of
recyclable polypropylene with a reinforcing inorganic mineral filler to
produce support modules
with suitable impact strength and elastic properties and fire retardant
properties for used.
In the preferred embodiment, each support structure has a shape and size
similar
to the support module shown in FIG. 1 and disclosed in U.S. Patent No.
4,905,437 and now
incorporated by reference. It should be understood, however, that the use of
recyclable
polypropylene and a mineral filler could be used to manufacture other types of
support structures
and components used with access floor systems.
As stated above, it is important that support structure used with access floor
systems have adequate modulus of elasticity and impact strength. Ideally, the
support modules
should have a modulus of elasticity of approximately 900 MPa and an impact
strength of
approximately 2.2 flt.lb./in.
In this invention, a recyclable polypropylene available as pellets is mixed
with 45
to 50% (wt/wt) of a mineral filler, such as talc or montmorillonite clay. The
purpose of the
mineral filler is to increase the support module's impact strength and modulus
of elasticity which
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is less that desired with recyclable polypropylene. Tests have also indicated
that one particular
type of mineral filler, montmorillonite clay, also provides flame retardant
properties to the
finished support structure. Tests have also shown that the adding or bonding
chemicals to the
polypropylene-filler composition can also increase the impact properties of
the support structure.
FIG. 3 shows a Table 3 that presents the results of twenty-two experiments
conducted on twenty-two samples (Experiments 9-30) with two recyclable
polypropylene
products, two inorganic mineral filler products, and two additive products.
The type of
concentrate and additive is indicated in the Additive column. The make up of
each composition
of polypropylene resin, mineral filler, and additive shown is shown in Table 2
shown in FIG. 2.
The two recyclable polypropylene products used were sold under the trademark
LONE STAR
111 by Lone Star Chemicals, located in Grapeville, Texas), and the trademark
PROFAX 6524.
These were two types of inorganic mineral filler used. The first four
concentrates
were made of 45 to 50% talc sold under the trademark NICRON 403 by Fitz Chem
Corporation.
The fifth and sixth concentrates were made of 50% montmorillonite clay sold
under the
trademark NANOCLAY.
Added to composition 2 was a polypropylene bonding additive (5%) sold under
the trademark Fusabond by Dupont Canada, Inc. of Ontario, Canada. Added to
compositions 3
and 4 was the bonding additive zinc sterate (3 and 5%, respectively).
In experiments 21 and 23, a nonoclay product was used that is sold under the
trademark NanoMax by Amcol International Corporation, Arlington Heights,
Illinois. The
NanoMax product is made of 50% nanoclay.
All of the experiments were conducted using an Instron 4400 universal testing
machine.
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In summary, the experiments clearly show that when 25 to 33% of talc or clay
filler was added to 66% (wdwt) of recyclable polypropylene resin, the
mechanical properties of
the finished product was favorably adjusted for use in an access floor system.
The experiments
also show that montmorillonite clay was especially beneficial.
In compliance with the statute, the invention described herein has been
described
in language more or less specific as to structural features. It should be
understood, however, that
the invention is not limited to the specific features shown, since the means
and construction
shown is comprised only of the preferred embodiments for putting the invention
into effect. The
invention is therefore claimed in any of its forms or modifications within the
legitimate and valid
scope of the amended claims, appropriately interpreted in accordance with the
doctrine of
equivalents.
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