U.S. patent application number 11/366786 was filed with the patent office on 2006-10-26 for thermoplastic pallet having foam-filled or foam-coated structural parts.
Invention is credited to Roy E. JR. Moore.
Application Number | 20060236903 11/366786 |
Document ID | / |
Family ID | 37185519 |
Filed Date | 2006-10-26 |
United States Patent
Application |
20060236903 |
Kind Code |
A1 |
Moore; Roy E. JR. |
October 26, 2006 |
Thermoplastic pallet having foam-filled or foam-coated structural
parts
Abstract
Improved structural parts of a thermoplastic plastic pallet
include foam, provided within hollows of the structural component
and/or upon the surfaces of the component to provide improved fire
resistance.
Inventors: |
Moore; Roy E. JR.;
(Killingworth, CT) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
US
|
Family ID: |
37185519 |
Appl. No.: |
11/366786 |
Filed: |
March 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10729615 |
Dec 5, 2003 |
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11366786 |
Mar 1, 2006 |
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09938954 |
Aug 24, 2001 |
6705237 |
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10729615 |
Dec 5, 2003 |
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60657488 |
Mar 1, 2005 |
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60227537 |
Aug 24, 2000 |
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Current U.S.
Class: |
108/57.25 |
Current CPC
Class: |
B65D 2519/00044
20130101; B65D 2519/00074 20130101; B65D 2519/00114 20130101; B65D
2519/00109 20130101; B65D 2519/00079 20130101; B65D 19/001
20130101; B65D 2519/00039 20130101; B65D 2519/00104 20130101; B65D
2519/00034 20130101 |
Class at
Publication: |
108/057.25 |
International
Class: |
B65D 19/38 20060101
B65D019/38 |
Claims
1. A plastic pallet, comprising a thermoplastic structural pallet
member including a foam thereon.
2. A plastic pallet in accordance with claim 1, wherein the
thermoplastic structural pallet member comprises polypropylene or
high density polyethylene.
3. A plastic pallet in accordance with claim 1, wherein the
structural pallet member is hollow and at least partially filled
with foam.
4. A plastic pallet in accordance with claim 3, wherein the
structural pallet member is a pallet column.
5. A plastic pallet in accordance with claim 3, wherein the
structural pallet member is a deck.
6. A plastic pallet in accordance with claim 3, wherein the amount
of foam is varied between different parts of the structural pallet
member.
7. A plastic pallet in accordance with claim 1, wherein the amount
of foam provided on the structural pallet member is varied along
different parts of the structural pallet member.
8. A plastic pallet in accordance with claim 3, wherein foam is
provided at least partially within a hollow of the structural
pallet member as well as on at least a portion of the exterior.
9. A plastic pallet in accordance with claim 1, wherein the foam is
a thermoset polymer foam.
10. A plastic pallet in accordance with claim 9, wherein the foam
is a polyurethane foam.
11. A plastic pallet in accordance with claim 9, wherein the foam
is a low density polyurethane foam.
12. A plastic pallet in accordance with claim 1, wherein the foam
is a ceramic or glass or expanded mineral foam.
13. A plastic pallet in accordance with claim 1, wherein the foam
further includes a fire retardant.
14. A plastic pallet in accordance with claim 13, wherein the foam
further includes 5-20 weight percent intumescent graphite .5-20
weight percent intumescent graphite.
15. A plastic pallet in accordance with claim 1, wherein the foam
covered section has a lower rate of heat release during a burn
test, as compared the same section without foam.
16. A plastic pallet in accordance with claim 1, wherein the foam
covered section has a higher impact strength, as compared the same
section without foam.
17. A plastic pallet in accordance with claim 1, wherein the pallet
comprises a metal deck and reinforcing beams in solid structural
plastic portions.
18. A plastic pallet in accordance with claim 1, wherein the
structural pallet member approximates the cross section shape of I,
H, C, or O.
19. A plastic pallet in accordance with claim 1, wherein the
structural pallet member includes lightening holes or filigree
structure.
20. A method of improving the fire resistance of a structural
plastic member of a pallet, comprising filling hollow portions of
the structural members with polymer foam or adhering polymer foam
to external surfaces of said structural members.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional patent
application Ser. No. 60/657,488, filed Mar. 1, 2005 and is a
continuation-in part of U.S. patent application Ser. No.
10/729,615, filed Dec. 5, 2003, which is a divisional of U.S.
patent application Ser. No. 09/938,954, filed Aug. 24, 2001, now
U.S. Pat. No. 6,705,237, which claimed priority to U.S. Provisional
patent application Ser. No. 60/227,537, filed Aug. 24, 2000, the
entire contents of each of which are specifically incorporated
herein by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a device for the transportation
of packaged goods, and, more particularly, to a pallet that meets
certain standards set by the Grocery Manufacturers Association
(GMA) and others for weight, durability, and strength.
BACKGROUND
[0003] One criterion which is used to evaluate plastic pallets is
to compare their performance to wood pallets, to find if they
perform equal or better than wood pallets under fire conditions. In
particular, Underwriters Laboratories (Northbrook, Ill., U.S.) has
developed a Standard, UL 2335, "Classification Flammability of
Plastic Pallets". The Standard is consistent with U.S. National
Fire Protection Association (NFPA) Standards 231 and 231 C, which
relate to warehouses and rack (pallet) storage of materials in
warehouses. Under the UL Standard, measurements are made of the
rate of spread of a fire within a stack of pallets, heat release,
and structural stability (resistance to collapse).
[0004] Most common thermoplastic materials, which may be used in
substitution of wood, have undesirable fire-related characteristics
compared to wood. On a typical equivalent article basis, the heat
release rate of the thermoplastic material is substantially greater
than wood, and the loss of strength and resultant structural
failure more rapid. Furthermore a plastic article can tend to melt
and form into a burning pool of liquid. Thus, it is found that the
existing conventional warehouse fire suppression systems (which are
generally designed for wooden pallets) can be inadequate and unsafe
with regard to plastic pallets.
[0005] What is needed in the art is a plastic pallet construction
having good fire resistance (which may approximate the fire
resistance of wooden pallets) that is also not too heavy, too
costly, and that does not lack the combination of mechanical
properties such as flexural strength and impact strength which a
successful pallet must have.
SUMMARY
[0006] The above described and other disadvantages of the prior art
are overcome and alleviated by the present thermoplastic pallet
comprising a plastic structural member including a foam thereon.
The thermoset foam may be provided on the exterior, on the
interior, or on both (e.g., when the structural member is hollow)
of plastic structural members.
[0007] In one exemplary embodiment, structural thermoplastic
members (e.g., polypropylene (PP) or high density polyethylene
(HDPE)), such as columns, have hollows which are filled with
thermoset foam. In another exemplary embodiment, the foam is a
thermoset plastic, such as polyurethane, which provides impact
strength to the hollow structural section. Other foams may also be
used. In another exemplary embodiment, the foam further includes a
fire retardant.
[0008] In another exemplary embodiment, thermoset foam is attached
to the exterior of a structural member. Both the interior foam
filling and exterior foam embodiments may be used together.
[0009] The foregoing and other objects, features and advantages of
the present pallet will become more apparent from the following
description of exemplary embodiments and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Referring now to the accompanying FIGURES, which are meant
to be exemplary and not limiting:
[0011] FIG. 1 is a partial cross sectional view of an exemplary
pallet column incorporating a foam therein;
[0012] FIG. 2 is a partial cross sectional view of exemplary foam
filled pallet deck and columns; and
[0013] FIG. 3 is a cross sectional view of an exemplary pallet
I-beam including a foam.
DETAILED DISCLOSURE
[0014] As is noted above, the presently described thermoplastic
pallet includes a foam material, which material by composition and
placement, impart fire-resistant to the thermoplastic pallet. By
"fire-resistant", as described herein, it is meant that the pallet
has a desirable combination of properties, including ignition,
burning rate, heat release rate, and retention of structural
strength, as such are observed when the pallet is subjected to
standard and non-standard fire test conditions. For example, the
presently described thermoplastic pallet will generate energy at a
lower rate than such pallet would otherwise generate.
[0015] A unique plastic pallet design comprising metal reinforcing
bars and other special features, to provide efficient design, and
to give strength to a pallet under normal and elevated temperature
conditions is described in copending U.S. patent application Ser.
No. 10/729,615. The pallet comprises several structural polymer or
metal elements that are assembled and then joined together. In an
exemplary embodiment, the pallet structure is made of polypropylene
(PP) or high density polyethylene (HDPE). The pallet may have metal
pieces as strengthening beams and a corrugated aluminum deck. The
assembly nature of pallet design makes it convenient to have
portions with differing material properties.
[0016] However, it is noted that in tests, the polyolefin
thermoplastics, and in particular common HDPE and PP have poor fire
resisting properties. By their nature they lose rigidity and
structural strength, and they melt and can form puddles of burning
plastic, when subjected to fire. The metal deck helps in providing
strength during burning, and the metal deck, compared to a plastic
deck, reduces the rate of heat release.
[0017] When there are structural sections of plastic, they may be
in cross sections which approximate the cross section shape of I,
H, C, O, etc., as appropriate, rather than being made solid, in
accord with good design to lighten weight and keep down the cost of
polymer and the pallet. Thus, a monolithic polymer beam may be made
in the above-described cross section shape. Lightening holes or
analogous filigree structure may be used in selected areas, such as
in the web of an I beam.
[0018] The pallet component shapes may be complex, but
approximations of those various features are used. However, insofar
as fire resistance is concerned, these approaches also have the
undesirable effect of providing a greater surface area of the
plastic member when it partially burns through, and that enhances
the propensity for burning in an oxidizing environment. The present
application provides a good solution to those undesirable effects
by selective application of foam to these structural
components.
[0019] Referring now to FIG. 1, a vertical cross section through a
plane, just off the center of an exemplary pallet is illustrated.
As illustrated, the exemplary pallet 20 has a base 36 comprising of
cross rails having internal metal beams 26A, 26B, and columns 34
running up from the base (exemplary column 34 is illustrated as
positioned at an outer edge 24 of pallet 20), which support a
rectangular frame 38, having internal metal beam 26T. A corrugated
metal deck 22 is mounted in the frame 38. It should be noted that
exemplary components are shown in simplified and conceptual manner.
The beams 26A, 26B, 26T are contained within solid plastic
sections. In an exemplary embodiment, the structural components
also include hollows. More particularly, the outer portion of the
frame 38 and the columns (of which in one exemplary embodiment,
there are eight around the periphery and one in the center) may be
hollow. The hollows 30 of the columns are illustrated as partially
or fully filled with foam, which in one embodiment may be a
semi-rigid closed cell polyurethane foam. Depending on the nature
of the hollows in the frame (with regard, e.g., to design for
impact resistance, etc.), and manufacturing limitations, hollows 32
in the frame may or may not be filled with foam.
[0020] Referring now to FIG. 2, another simplified and exemplary
configuration of pallet 20A is illustrated, wherein the deck 22A
and columns (or feet) 34 are comprise hollow structural plastic. A
foam is provided within the hollow portions of the deck 22A and
columns 34. It should be noted that filling the hollow portions of
the pallet with semi-rigid foam may provide increase in bending or
column strength (particularly with regard to the present
embodiment). Also, a significant increase in impact strength may be
achieved.
[0021] Any of the foam described herein may optionally include fire
retardants (it being understood that the presently described
structural components including foam are beneficial without flame
retardants). That result can be attributable to the fact that when
the foam is confined within the structural plastic which defines
the portion of the pallet, the portion acts largely as it would if
it were solid. The foam tends not to melt when burning to the
extent that the structural plastic would. And of course, being
largely void, it has less mass. Furthermore it is insulative.
Second, if there is bum-through of the structural exterior, the
fire spreads less slowly in the interior because the foam inhibits
oxygen and heat from reaching the other interior surfaces of the
structure. Thus, the rate of burning and heat evolution of a hollow
structural element is thus inhibited by putting foam inside of a
hollow article. The amount of foam can also be varied along the
length of a member, so that a controlled collapse of the pallet can
be achieved, where it may be desirable to collapse part or all of a
burning pallet to reduce exposed surface area and consequently
reduce the amount of pallet burn.
[0022] In one exemplary embodiment of the invention, a hollow
structure of HDPE or PE (for example the column 34 of FIG. 1),
having a wall thickness of 0.050 to 0.200 inch, is filled Class I
polyurethane foam having a density of 2 to 4 lbs per cubic foot
(for example, such as is supplied by BASF, Livonia, Mich.). The
foam may completely or partially fill the hollow portions and/or
may cover the exterior.
[0023] If a fire retarding additive is used in the foam, an
exemplary material is Grafguard intumescent graphite material. The
fire retarding additive may be mixed into the the polymer material,
e.g., polyurethane, which will comprise the foam before it is
"shot" or injected into the hollow spaces. In one embodiment, the
intumescent additive content is 5-20 weight percent. Analogously
with amount of foam, the amount of fire retardant can be controlled
according to the burning behavior which is sought. Other substances
may also be incorporated into the foam, as desired.
[0024] The foam which is used will provide a thermoplastic section
of the pallet with improved burn test heat release characteristic;
and preferably improved impact strength. When a structural element
is exposed to fire generally, or ignited at one end, the rate of
burning is decreased compared to when foam is not used. Where there
is foam, it is first of all insulative. Second, its character upon
burning, that it remains substantially in place inhibits oxygen and
heat from reaching the surface of the HDPE structural element.
Thus, when there is a hollow element filled with foam, even though
part of the skin burns away, say at the first end which is ignited,
the flame will only progress according to the oxygen which reaches
the element on its unprotected exterior, since the interior foam
greatly inhibits such on the interior. Thus, the element, and the
article as a whole, is found to burn more slowly, which means its
rate of heat release is desirably less, in fulfillment of meeting
the aims of the UL Standard. Likewise, a structure which heats and
burns more slowly will retain its structural strength for a longer
time. Other foam materials, and other porous materials, known in
the art which behave as described may be alternatively used in
substitution of a thermoset foam or in combination with it. For
example, ceramic or glass or expanded mineral foams may be used as
fillers within a thermoset or other foam, or by themselves.
[0025] In another exemplary embodiment, a molded column 34 of a
pallet, having exemplary dimensions of 8.times.5.times.6 inches, is
filled with foam. The foam may be placed within the hollow sections
by injection after the pallet is formed, including by use of the
techniques where nubs or feet seal the holes of injection at the
bottom of a pallet column.
[0026] Referring now to FIG. 3, another exemplary embodiment
illustrates a thermoplastic structural element comprising an I-beam
section 30 that is partially or fully covered with foam 42. In one
exemplary embodiment, the foam is a low density polyurethane foam
(or other composition foam exhibiting comparable properties)
adhered to the surface of the structural element. The foam on the
exterior may be somewhat less effective than filled interior
embodiments, and the foam may be susceptible to mechanical damage,
but a significant benefit in burning characteristic is still
realized. As noted above, foam may also be placed on the interior
and exterior of a hollow member.
[0027] It should be apparent that to the extent inclusion of a fire
retardant chemical is economic, does not significantly raise
weight, and is otherwise acceptable, it may be included in the foam
and will likely enhance performance of the foam.
[0028] Although this invention has been shown and described with
respect to exemplary embodiments, it will be understood by those
skilled in this art that various changes in form and detail thereof
may be made without departing from the spirit and scope of the
claimed invention.
* * * * *