U.S. patent application number 11/366785 was filed with the patent office on 2006-11-09 for fire resistant thermoplastic pallet.
Invention is credited to Ronald P. Brochu, James J. Burnes, Roy E. JR. Moore, Daniel J. Swistak.
Application Number | 20060249058 11/366785 |
Document ID | / |
Family ID | 37392945 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060249058 |
Kind Code |
A1 |
Moore; Roy E. JR. ; et
al. |
November 9, 2006 |
Fire resistant thermoplastic pallet
Abstract
The presently disclosed thermoplastic pallet advantageously
incorporates fire resistance by virtue of one or more of the
following aspects: a sprinkler friendly deck or frame; variable
fire retardant or coating distributions; fire collapsible cross
beams; foam filled or foam coated parts; and pallet design,
including proportioning amounts of plastic and metal utilized in
construction. Exemplary combinations of features enables the pallet
to meet all the dimensional, mechanical behavior and burn test
requirements. The use of metal components including a corrugated
aluminum deck having specially position through holes for sprinkler
water, and the engineered placement of hollows in the structural
plastic parts enables a reduction in the amount of plastic, and the
amount of fire retardant in what plastic there is and in the pallet
as a whole.
Inventors: |
Moore; Roy E. JR.;
(Killingworth, CT) ; Brochu; Ronald P.; (Richmond,
KY) ; Swistak; Daniel J.; (Newmarket, NH) ;
Burnes; James J.; (Chester, CT) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
US
|
Family ID: |
37392945 |
Appl. No.: |
11/366785 |
Filed: |
March 1, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10729615 |
Dec 5, 2003 |
|
|
|
11366785 |
Mar 1, 2006 |
|
|
|
09938954 |
Aug 24, 2001 |
6705237 |
|
|
10729615 |
Dec 5, 2003 |
|
|
|
60657484 |
Mar 1, 2005 |
|
|
|
60657678 |
Mar 1, 2005 |
|
|
|
60657488 |
Mar 1, 2005 |
|
|
|
60227537 |
Aug 24, 2000 |
|
|
|
Current U.S.
Class: |
108/57.25 |
Current CPC
Class: |
B65D 2519/00562
20130101; B65D 2519/00437 20130101; B65D 2519/00557 20130101; B65D
2519/00338 20130101; B65D 2519/00442 20130101; B65D 2519/00044
20130101; B65D 19/0026 20130101; B65D 2519/00333 20130101; B65D
2519/00034 20130101; B65D 2519/008 20130101; B65D 2519/00024
20130101; B65D 2519/00079 20130101; B65D 2519/00343 20130101; B65D
2519/00323 20130101; B65D 2519/00318 20130101; B65D 2519/00288
20130101; B65D 2519/0086 20130101 |
Class at
Publication: |
108/057.25 |
International
Class: |
B65D 19/38 20060101
B65D019/38 |
Claims
1. A fire resistant thermoplastic pallet; comprising: a pallet deck
supported over a pallet base, wherein at least one of said deck and
base comprise a thermoplastic material configured to be fire
resistant by virtue of two or more of: fire sprinkler water holes
provided therein, variable fire retardant or coating distributions,
fire collapsible components, and foam filled or foam coated
parts
2. A fire resistant thermoplastic pallet in accordance with claim
1, further comprising a corrugated deck supported over a base, the
deck having at least one hole in a valley of a corrugation, wherein
the flow area of said at least one hole is located over a part of
the base of the pallet.
3. A fire resistant thermoplastic pallet in accordance with claim
2, wherein when said pallet rests on a level surface, said at least
one hole is located in a lower region of said corrugation, such
that water landing in another portion of said corrugation will tend
by gravity to run towards the portion of said corrugation
containing said hole.
4. A fire resistant thermoplastic pallet in accordance with claim
2, wherein a plurality of corrugations are interconnected.
5. A fire resistant thermoplastic pallet in accordance with claim
4, wherein said plurality of corrugations are interconnected via
staggered channels.
6. A fire resistant thermoplastic pallet in accordance with claim
2, wherein when said pallet rests on a level surface, an outer
length of said deck supporting frame is either higher than a hole
in said deck supporting frame or higher than said deck, such that
water will tend to flow toward said hole or toward said deck from
said outer length of said deck supporting frame rather than flowing
over the outer length of said deck supporting frame.
7. A fire resistant thermoplastic pallet in accordance with claim
6, wherein said deck supporting frame includes a plurality of
holes, which holes are provided in portions of said deck supporting
frame that are lower than an outer length of said deck supporting
frame and lower than portions of said deck, such that water will
tend to collect or flow between said plurality of holes in said
deck supporting frame.
8. A fire resistant thermoplastic pallet in accordance with claim
1, comprising a plurality of thermoplastic portions, wherein at
least two of said portions have differential fire resistance, by
virtue of compositions or coatings, according to the position or
geometry of said portions.
9. A fire resistant thermoplastic pallet in accordance with claim
8, wherein wherein at least one said portion is thinner or has a
higher surface area to volume ratio relative to another of said
portions.
10. A fire resistant thermoplastic pallet in accordance with claim
8, wherein a deck of the pallet has higher fire retardant content
than columns upon which the deck is mounted.
11. A fire resistant thermoplastic pallet in accordance with claim
8, wherein part or all of the periphery of a deck has less
retardant or no retardant, compared to the interior of the deck
which has fire retardant.
12. A fire resistant thermoplastic pallet in accordance with claim
1, wherein the pallet is storable in a rack having opposing side
rails, by resting opposing lengthwise edges of the pallet on the
rails, the pallet comprising a plastic portion configured to span
the distance between the rails of the rack, wherein at least one
cross beam is secured on or within said plastic portion, the cross
beam and plastic portion configured such that said cross beam and
plastic portion will structurally fail upon exposure to heat from a
fire.
13. A fire resistant thermoplastic pallet in accordance with claim
12, wherein said at least one cross beam has a length and location
within the pallet, so that one end of the beam is configured such
that it is inward from the lengthwise edge of the pallet and inward
from the vertical extension of the inner edge of the rail of the
storage rack, and wherein, when the plastic portion softens, the
end of the beam will fall downwardly from the rack.
14. A fire resistant thermoplastic pallet in accordance with claim
12, wherein said at least one cross beam has a length and location
within the pallet, so that both ends of the beam are configured
such that they inward from the lengthwise edges of the pallet and
inward from the vertical extension of the inner edges of the rail
of the storage rack, and wherein, when the plastic portion softens,
an end of the beam will fall downwardly from the rack.
15. A fire resistant thermoplastic pallet in accordance with claim
12, wherein said at least one cross beam includes at least one
reinforcing material engineered to degrade when exposed to heat
from a fire, such that the reinforcing beam will fail upon exposure
to heat from a fire.
16. A fire resistant thermoplastic pallet in accordance with claim
1, comprising a thermoplastic structural pallet member including a
foam thereon.
17. A fire resistant thermoplastic pallet in accordance with claim
16, wherein the thermoplastic structural pallet member comprises
polypropylene or high density polyethylene.
18. A fire resistant thermoplastic pallet in accordance with claim
16, wherein the structural pallet member is hollow and at least
partially filled with foam.
19. A fire resistant thermoplastic pallet in accordance with claim
18, wherein the structural pallet member is a pallet column.
20. A fire resistant thermoplastic pallet in accordance with claim
18, wherein the structural pallet member is a deck.
21. A fire resistant thermoplastic pallet in accordance with claim
16, wherein the amount of foam is varied between different parts of
the structural pallet member.
22. A strong burn-resisting pallet, predominately composed of
thermoplastic, for transporting goods, comprising: a base, made of
thermoplastic, such as polyethylene or polypropylene, comprising
rails between columns, the rails having reinforcing beams within; a
multiplicity of columns running upwardly from the base; each of
said multiplicity having a thermoplastic shell exterior, and filled
with foam; a top, attached to the tops of the columns, comprising a
circumscribing thermoplastic frame, mounted on the columns; and a
metal deck, attached to and running across the interior opening of
the frame; the deck having a plurality of through holes for water
drainage, so the water drops onto plastic parts of the bottom of
the pallet and onto any pallets mounted below.
23. A pallet in accordance with claim 22, wherein the plastic of
the rails, columns and frame contain fire retardant.
24. A pallet in accordance with claim 22, wherein the pallet weighs
no more than 55 pounds, wherein the thermoplastic material
(including any additive such as fire retardant) is 70% of the
weight or less.
25. A pallet in accordance with claim 22, having a corrugated and
perforated aluminum sheet metal deck which weighs between about
about 5 and 7 pounds, and steel beams weighing between about 12 and
13 pounds.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Nos. 60/657,484, filed Mar. 1, 2005; 60/657,678, filed
Mar. 1, 2005; 60/657,488, filed Mar. 1, 2005, U.S. patent
application Ser. No. (number not assigned), filed Feb. 18, 2008,
entitled "Fire Sprinkler Friendly Pallet", which claimed priority
to U.S. Provisional Patent Application Ser. No. 60/654,764, filed
Feb. 18, 2005, and U.S. patent application Ser. No. (number not
assigned), filed Feb. 18, 2005, entitled "Fire Collapsible Cross
Beamed Pallet", which claimed priority to U.S. Provisional Patent
Application Ser. No. 60/654,759, filed Feb. 18, 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] Pallets, both bearing goods and empty, are often stored on
racks in warehouses which are fitted with fire-fighting automatic
sprinkler systems. The heat and rate of combustion of the pallets
made of typical polyethylene or polypropylene pallet material are
inherently high compared to traditional wood pallets. A bad
conflagration can result, overwhelming the sprinkler system of a
typical warehouse, many of which were designed for wood pallets.
Adding additional sprinkler systems, or having special areas for
plastic pallets, involves substantial unwanted costs or logistics
problems.
[0004] A criteria 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 231C, which
relate to warehouses and rack (pallet) storage of materials in
warehouses. Under the UL Standard, a group of stacked pallets is
artificially ignited in a certain defined containment building.
Measurements are made of the rate of spread of a fire within a
stack of pallets, the amount of heat released during burning of the
stack (gauged by the number of standard sprinkler heads which are
triggered in the test setup), and the structural stability
(resistance to collapse) of the stack.
[0005] Plastic pallets have been in use, but have not gained wide
acceptance, since they have not met all the criteria for pallets.
Generally, pallets must have certain dimensions, be strong enough
to carry specified loads, must not be too heavy, and must be
durable in resisting damage during use, as measured by certain
tests and field use. In particular, to be accepted, they must meet
standards of the Grocery Manufacturers of America (GMA). Among the
criteria in the standard are that pallets have fire resistances,
sufficient to not exceed the heat release set by Underwriters Lab
Standard 2335 when intentionally set on fire in a test facility, to
simulate a warehouse fire. The pallet also must not be too heavy,
must be strong enough to carry specified loads, and must be durable
in resisting damage during use, as measured by certain tests and
field use. So far, no pallet has been able to meet all these
criteria. Indeed, the more fire retardant included in the plastics,
the more fragile the plastic. Thus, other approaches are sought.
And of course, cost is important. It has been a stumbling block for
pallets to meet the foregoing mechanical and cost criteria to also
meet fire resistance standards. One accepted criterion is that,
pallets in a rack, subjected to a fire test which simulates a
warehouse fire, cannot burn in a way such that they exceed the
maximum heat release (heat of combustion in any 10 minute time
span) set by Underwriters Lab Standard 3435.
[0006] One solution may appear to be making pallets out of fire
resisting plastics, such as Noryl plastic for pallets described and
offered by General Electric Co., or such as polypropylene or
polyethylene containing significant amounts of fire retardants.
However, taking that approach that creates several problems. They
variously include additional weight, reduced strength, the toxicity
and environmental unacceptability of many of the good fire
retardant additives, and increased cost.
[0007] What is needed in the art is a low cost, low weight,
durable, fire resistant pallet.
SUMMARY
[0008] The above-described and other problems and disadvantages of
the prior art are overcome and alleviated by the present
thermoplastic pallet. The presently disclosed thermoplastic pallet
advantageously incorporates fire resistance, while retaining
durability, low weight and low cost. Such fire resistance is gained
by virtue of one or more of the following aspects: a sprinkler
friendly deck or frame; variable fire retardant or coating
distributions; fire collapsible cross beams; foam filled or foam
coated parts; and pallet design, including proportioning amounts of
plastic and metal utilized in construction. Exemplary combinations
of features enables the pallet to meet all the dimensional,
mechanical behavior and burn test requirements. The use of metal
components including a corrugated aluminum deck having specially
position through holes for sprinkler water, and the engineered
placement of hollows in the structural plastic parts enables a
reduction in the amount of plastic, and the amount of fire
retardant in what plastic there is and in the pallet as a
whole.
[0009] The above-described and other features will be appreciated
and understood by those skilled in the art from the following
detailed description, drawings and appended claims.
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 semi-schematic elevation view illustrating
pallets stored on a rack in a warehouse having sprinklers;
[0012] FIG. 2 is a partial vertical cross-sectional view of an
exemplary pallet including corrugations having holes;
[0013] FIG. 3 is a perspective cutaway view of an exemplary pallet
including corrugations having holes;
[0014] FIG. 4 is a perspective cutaway view of an exemplary pallet
having interconnected corrugations having holes;
[0015] FIG. 5 is a perspective cutaway view of an exemplary pallet
having corrugations interconnected with an angled deck supporting
frame having holes;
[0016] FIG. 6 is a partial vertical cross-sectional view of an
exemplary pallet having contoured base portions;
[0017] FIG. 7 is a partial vertical cross-sectional view of another
exemplary pallet having contoured base portions;
[0018] FIG. 8 is a partial vertical cross-sectional view of another
exemplary pallet having contoured base portions;
[0019] FIG. 9 is a cross sectional view of an exemplary pallet;
[0020] FIG. 10 is a cross sectional view of an exemplary pallet
column;
[0021] FIG. 11 is a cross sectional view of an exemplary pallet
column and deck;
[0022] FIG. 12 is a cross sectional view of an exemplary pallet
corner;
[0023] FIG. 13 is a cross sectional view of an exemplary pallet
deck;
[0024] FIG. 14 is a cross sectional view of an exemplary pallet
component mold;
[0025] FIG. 15 shows a bottom side of an exemplary plastic pallet
having an array of beams which are embedded in the bottom of the
pallet;
[0026] FIG. 16 shows a detail of the top cross section view of an
exemplary pallet corner;
[0027] FIG. 17 is a vertical elevation end view of exemplary pallet
supported in a warehouse rack along its opposing lengthwise
ends;
[0028] FIG. 18 is a front elevation view of an exemplary beam
incorporated in a pallet;
[0029] FIG. 19 is a bottom view of a pallet incorporating a
plurality of exemplary beams;
[0030] FIG. 20 is a bottom view of a pallet incorporating a
plurality of exemplary beams;
[0031] FIG. 21 is a bottom view of a pallet incorporating a
plurlity of exemplary beams;
[0032] FIG. 22 is a cross sectional view of an exemplary tubular
beam and connector;
[0033] FIG. 23 is a cross sectional view of an exemplary tubular
beam construction;
[0034] FIG. 24 is a partial cross sectional view of an exemplary
pallet column incorporating a foam therein;
[0035] FIG. 25 is a partial cross sectional view of exemplary foam
filled pallet deck and columns;
[0036] FIG. 26 is a cross sectional view of an exemplary pallet
I-beam including a foam; and
[0037] FIG. 27 is a partial perspective view of an exemplary fire
resistant pallet.
DETAILED DESCRIPTION
[0038] The presently disclosed thermoplastic pallet advantageously
incorporates fire resistance, while retaining durability, low
weight and low cost. Such fire resistance is gained by virtue of
one or more of the following aspects: a sprinkler friendly deck or
frame; variable fire retardant or coating distributions; fire
collapsible cross beams; foam filled or foam coated parts; and
pallet design, including proportioning amounts of plastic and metal
utilized in construction. Sprinkler friendly decks or frames are
described with regard to FIGS. 1-8. Variable fire retardant or
coating distributions are described with regard to FIGS. 9-14. Fire
collapsible cross beams are described with regard to FIGS. 15-23.
Foam filled or foam coated parts are described with regard to FIGS.
24-26.
[0039] Referring now to FIG. 1, a semi-schematic elevation view
illustrates pallets stored on a rack in a warehouse having
sprinklers. Pallets 20C are illustrated as provided singly,
stacked, and loaded with goods 24, wherein the pallets are stored
on racks 22 which comprise opposing side columns 22L and 22R and
horizontal rails 34 which are spaced apart to receive the opposing
edges of the pallets. The ceiling 30 of the warehouse is fitted
with a firewater plumbing system comprising pressurized water pipes
28 and sprinkler heads 26. For typical sprinkler heads, when the
ceiling temperature rises above a predetermined design point,
established by selection of a low melting point metal that
restrains a spring-loaded water valve, the sprinkler heads open and
discharge a volume of water W in the form of sprays 32. The spray
water falls generally downwardly, to land on the stored pallets
below. The aim is to cool the burning objects below the point of
ignition, and to prevent non-burning objects from rising to such
point.
[0040] Referring now to FIG. 2, as illustrated by the partial
vertical cross section of a pallet 20, the pallet deck 46 of an
exemplary pallet 20 is corrugated for strength. Through-holes 40
receive water W within the valleys 45 of corrugations and pass
water W to structures 44C below the pallet deck 46, thus cooling
those structures below. The edge of a pallet 20 rests on the rail
34 of a rack 22L. It is to be understood that the term corrugation
or corrugated should encompass any surface topography that includes
at least one channel, groove, depression or valley along which
water can be channeled or contained. Additionally, the base of the
pallet includes any portions of the pallet below the top surface of
the pallet, which top surface may include the deck and the top
portions of the frame.
[0041] Referring now to FIG. 3, exemplary pallet deck 46, which may
comprise metal, metal alloy, plastic or other material, is attached
to rectangular plastic frame 48 of pallet 20. The frame 48 is
mounted on columns 42, 42C which run down to the base comprising
outer rails 44 shaped as a rectangle and cross rails 44C which run
to and from the midpoints of rails 44, crossing at center column
42C. Metal beams, not shown, or other reinforcing components may be
provided within the rails and frame 48 for strength as in U.S. Pat.
No. 6,705,347, the disclosure of which is incorporated herein by
reference. As in FIG. 2, the exemplary pallet deck 46 has a
multiplicity of corrugations for strength which comprise
depressions or valleys 45.
[0042] With reference to FIGS. 2 and 3, through-holes 40 are
located at the bottom of valleys 45 of the deck. The holes are
selectively located over the rails 44C or whatever other structure
comprises a lower portion of the pallet. There may be other holes
which are not above rails or other bottom structure, for drainage.
For instance, if there is a corrugation depression which does not
lie above a rail, that corrugation could be fitted with a hole.
[0043] Thus, at least part of the water W which lands on the pallet
during a fire, either from sprinklers, or from another pallet
stacked above, flows through the specially-positioned holes 40, so
the water lands on a thermoplastic rails 44C or other structure
which comprise the base of the pallet, to suppress or prevent
burning. Improved performance has been seen in the aforementioned
Underwriter Laboratories tests. Should a pallet have a continuous
bottom deck construction, then holes can likewise be placed in the
bottom deck. The valleys 45 may be sloped slightly along their
length, so water runs downwardly toward the holes 40.
[0044] With reference to FIG. 4, another exemplary embodiment is
illustrated at 20A. At least some of the corrugations of the deck
are connected by connector channels 50, to help distribute the
water amongst the different valleys 45. Such configuration tends to
even water flow into holes 40, when the water falls unevenly on the
surface of the deck. The connectors 50 may also be staggered from
valley to valley, for best deck strength.
[0045] Referring now to FIG. 5, part of an exemplary corner of a
pallet is illustrated. In one exemplary embodiment, frame 48A,
which supports deck 46, has through holes 52, which are configured
to drop water on the outer rails 44 of the base. In another
exemplary embodiment, the top surface of the outer part of the
frame is sloped inwardly toward the center at slight angle Z. In
such embodiment, water falling on outer portions of said deck
supporting frame will tend to run to inner portions of said deck
supporting frame. The top surface of the frame may also provide a
gutter 60, so water will flow lengthwise along the frame, as
suggested by the arrows. Water flows to the locations of holes 52
which are positioned above base rails 44, as they run between the
columns. The water drops onto the base rail 44, and from there onto
any pallet below. Thus water which lands on, or flows over typical
frame surface portion 56, which is over the corner column 42 (not
shown in FIG. 5), is usefully directed onto the base or other lower
portions of the pallet. In addition, peripheral connector channels
58 may be used to allow water in some of the valleys 45 to flow
onto the top of the frame and into the gutter.
[0046] In other exemplary embodiments, the top surface of rails 44,
44C may be usefully shaped to help fire resistance. Referring now
to FIG. 6, rail 44A is provided with a slope, which directs water
towards internal portions of the pallet or ensures that water will
flow through lower portions of the pallet to goods or additional
pallets below, rather than allowing water to possibly flow outward,
as when the rail 44a is flat or fully crowned. Referring now to
FIG. 7, exemplary rail 44B has a surface which is concave or
grooved, such that water flows through holes 62 provided in lower
portions of rail 44B and onto goods or additional pallets below,
rather than allowing water to possibly flow outward. Similarly,
FIG. 8 illustrates an exemplary rail 44E having a corrugated
surface for the similar purpose. Such base portion surface
contouring, which contouring selectively directs water, may
similarly be applied to base portions provided underneath holes in
said deck.
[0047] It should be noted that the perforations in the deck and
other parts of the pallet need not be round. For example, slots,
among other configurations, may be used. At any location, more than
one hole may be placed. The holes may also be of various sizes. As
should be evident, the different features described can be combined
with each other. Pallet materials may comprise plastics, metals,
wood, and the like, as well as combinations of the foregoing.
[0048] Accordingly, the present disclosure provides, in part, a
water flow control system for a pallet, which selectively directs
water deposited on upper surfaces of a pallet by fire sprinkler
systems to lower portions of the pallet that may gain additional
fire resistance from exposure to such water.
[0049] Solid particulate fire retardants may also be included in
the thermoplastic pallet compositions, for example Grafguard
graphite intumescent material, aluminum trihydrate, magnesium
hydroxide or antimony trioxide (often used with bromine compounds),
among others. The solid fire retardants may be used in combination
with other types of fire retardants, for instance, brominated
hydrocarbons. It will be appreciated that the invention may be
applied to the inclusion of other ingredients, solid particulate or
not, in a pallet and to other articles.
[0050] The present invention also recognizes that addition of fire
retardants in quantities sufficient to impart minimal to good fire
resistance, which in one embodiment, and depending on the material,
ranges from 10 to 30 weight percent retardant, correspondingly
decreases the fracture toughness of that article. In the example of
plastic pallets, the pallet becomes too prone to breakage,
particularly around the edges of the pallet where the shanks of the
tines of a forklift truck may impact the pallet. Accordingly, an
improved article is described, wherein fire resistance of the
article is selectively tailored with regard to the geometry and/or
position of a component of the article.
[0051] Referring now to FIGS. 9-13, partial vertical cross sections
of portions of exemplary thermoplastic pallets are illustrated.
Referring to FIG. 9, exemplary pallet 220 comprises a deck 222,
which is welded to the columns 226 of base 224. In this exemplary
embodiment, the deck includes a plurality of holes (the deck may
take other configurations, e.g., solid or grid-like, among others).
The columns 226, which have hollows at their top ends, are
interconnected by rails 230. Hollow square cross section metal
beams 228 are within the rails. In one exemplary embodiment, deck
222 of pallet 220 has a higher concentration of retardant relative
to the frame 224. As an example, HDPE deck has 10% intumescent
composition, and the frame has 5%. (All concentrations are by
weight unless otherwise indicated.)
[0052] Referring now to FIG. 10, a portion of exemplary pallet 222A
is illustrated, wherein beam 228 is covered by a floor plate 229.
In an exemplary embodiment, the plate 229 is configured to
incorporate of the beam 228 within the base and comprises no or low
fire retardant relative to other portions of the pallet. In such
embodiment, the beam 228 is strategically engineered to fail in the
event of a fire. This is due to the lack of significant fire
retardant in the plate 229. At an early stage in a fire, the beam
228 will be subjected to heat and will fail according to engineered
design.
[0053] Referring now to FIG. 11, an exemplary pallet 220B is
illustrated, wherein such pallet lacks base rails. An exemplary
deck is a two-layer composite structure, which may be made for
example by co-extrusion, by joining one sheet to another, or by
injection molding, among other methods. In one embodiment, the
underside layer 227 comprises a first composition with a large
amount of fire retardant relative to the top layer 225. Such
exemplary configuration provides durability for the top of the
deck, but at the same time provides fire protection to the pallet
(oftentimes flames will rise up from below, and the lower deck
layer provides a lower barrier relative to heat sources from above
as well). Other layers may also be interposed between the top and
bottom layers, for other properties or fire resistance. The layers
may also be contoured to create cavities therebetween, and the
cavities may be filled with foam, such as urethane.
[0054] Referring now to FIG. 12, opposing edges of an exemplary
pallet 220D is illustrated, wherein deck 222D has an inner portion
comprising a first material having fire retardant (and thus
diminished impact or other properties) and an integral edge portion
242 with less fire retardant and better impact properties. In
another exemplary embodiment, the edge portion that has minimal or
no fire retardant at least spans the openings that are between
columns 226D, through which forks enter the space under the pallet
for transport.
[0055] Referring not to FIG. 13, a top view of exemplary pallet
220C is illustrated, wherein deck 222C has a central area 234 with
higher retardant content than a periphery portion 232. The dashed
boundary line 233 is one exemplary indication of where the
composition changes. Depending on the manufacturing technique that
is used, and the objective, the demarcation of composition change
may be definite or gradual. While the periphery of the deck may be
thin and thus should have fire retardant in accord with another
teaching herein, the volume of plastic, which has the inferior fire
retardant, is a small fraction of the total pallet. Thus, while
burn test performance might be somewhat reduced the performance can
still be acceptable, and the "give up" is well traded against
durability and strength, in considering the total pallet
design.
[0056] It is noted that rather than varying the pallet composition,
a fire resistant or reflective coating may be applied to portions
of the pallet. In another exemplary embodiment, part or all of the
pallet surface is coated with a heat reflective material.
Additionally, selected under-side exposed surfaces of the pallet
may be coated with the heat reflective surface. In an exemplary
embodiment, a thin layer of aluminum or other shiny metal is vapor
deposited, using well know technology, on the selected surfaces of
the plastic. Alternately, aluminum metal foil can be adhered to the
surface of the plastic. Thus, the amount of thermal radiation
received from adjacent pallets or other materials which may be
burning is reduced. The time for the coated pallet portion to rise
in temperature and ignite is increased, resulting in improved
fire-resisting characteristic.
[0057] Referring now to FIG. 14, a simplified cross section view of
an exemplary mold for a pallet other dual property object is
illustrated. The exemplary cavity parts 226CC, 232CC and 234CC are
illustrated as corresponding to numeral parts of exemplary pallet
220C. The mold comprises two mating parts 236, 238. When installed
in a molding machine, injection mold nozzles feed molten plastic
through ports 254, 256. Two different material compositions, one
with high retardant content, the other with low or no retardant
content are provided by two different sets of nozzles, fed by
appropriate injection extruders and supplies. The low content
material is injected in the ports 254 while the high content
material is injected in the ports 256. In another exemplary
manufacturing alternative, with reference to FIG. 13, the deck
parts 234, 232 may be separately fabricated and then joined
together, as by welding.
[0058] The presently disclosed pallet recognizes that when there is
a warehouse fire involving molded plastic pallets which are stacked
one above another in a warehouse rack, the rate of heat output will
be mitigated if the surface area of plastic pallet material which
is exposed to flames is reduced. Thus, as described by exemplary
embodiments herein, a pallet subjected to the heat of a fire
desirably fails and falls from the rack. Such pallet may fall onto
an underlying pallet and goods, or onto the floor. When multiple
pallets sandwich together, the exposed surface area of burnable
material will be reduced, and the access of oxygen bearing
atmosphere is inhibited.
[0059] Referring now to FIG. 15, a bottom side of an exemplary
plastic pallet 120 is illustrated, wherein an array of beams is
embedded in the bottom of the pallet. Without being limited, pallet
120 may be constructed in accord with the aforementioned commonly
owned U.S. Pat. No. 6,705,237 to Moore et al., the disclosure of
which is hereby incorporated by reference. The embedded beams are
represented in this and other figures by dashed lines.
[0060] Referring still to FIG. 15, the exemplary beam array
comprises lengthwise beams 124 and cross beams 126. (Length and
width are arbitrary in this disclosure, except that a pallet is
considered to mount in a rack with its length parallel to the rails
130 of the rack.) In one embodiment, the beams are perforated steel
box beams. In another exemplary embodiment, the beams run around
the rectangular periphery of the pallet. In another exemplary
embodiment, the beam ends are close to each other, but the beams
are not structurally attached to each other.
[0061] Referring now to FIG. 16, a detail of the top cross section
view of an exemplary pallet corner is illustrated. The beams cross
in the center of the pallet. The beams may be in the base and top
frame of the pallet and are generally parallel to the plane of the
pallet, that is to the plane of the goods-carrying deck 134 at the
top of the pallet.
[0062] In one exemplary embodiment, the pallet has a metal deck. In
such embodiment, beams are provided in the rails which comprise the
base of the pallet. While the above describes exemplary metal
reinforcing beams, beams made of other materials, for example
composite plastic materials, such as graphite reinforced plastic,
or some strong ceramic, may be used. The beam is, in general terms,
a member, partially or fully surrounded by the thermoplastic of the
pallet (though not necessarily embedded therein), having
substantially different properties, in particular, higher elastic
modulus and tensile strength.
[0063] Referring now to FIG. 17, a vertical elevation end view of
exemplary pallet 120 is illustrated as supported in a warehouse
rack along its opposing lengthwise ends 136. The opposing sides 136
of the pallet rest on opposing side lips of L-shape cross section
rails 130 of an exemplary pallet storage rack. Without being
limiting, the distance between the inner edges of the racks, RL, is
typically about 42 inches, to receive a typical pallet which is 48
inches wide.
[0064] Referring still to FIG. 17, in another exemplary embodiment,
the cross beams 126 have a length LB which is less than the spacing
RL between the rails, and the beams are centered between the
opposing lengthwise sides 136. Thus, there is a gap G between the
vertical extension of the ends of the beams and the vertical
extension of the inner edges of the lips of the pallet rack. As
used herein, a beam which is shorter than the width between the
rack edges is called a "short beam". Of course, there is some
clearance between the vertical sides of the rails of the rack and
the outside edges of the pallet. Thus, in another exemplary
embodiment, the lengths of beams 126 are sufficiently short to
accommodate the resultant play or possible shifting from side to
side of a pallet mounted in the rack. Thus, in all cases with
regard to this exemplary embodiment, the end of a beam 126 will not
be above the vertical extension of the innermost edge of the rail.
In other exemplary embodiments, e.g., where one end may extend
beyond said vertical extension, and the other does not, the length
and/or position of the beams may chosen accordingly to anticipate
shifting within the rack.
[0065] In accordance with the above exemplary embodiments, in the
event of a fire, the plastic of the pallet softens and loses
strength, and or burns away, and cross beam 126 will no longer be
supported at one or both of its ends. As the plastic softens or
disappears, the one end of the pallet will fall from the rail, and
the pallet will collapse into the space between the rails.
[0066] Referring now to FIG. 20, in another exemplary embodiment,
at least one beam 26A is offset (although all beams may be) from
one lengthwise edge so that one end of the beam is vertically above
the rack rail, but the other end is not. In this exemplary
embodiment, the cross beams may be short beams, or they may have
lengths which are equal or greater than the space between the rail
inner edges.
[0067] As illustrated in FIG. 15, lengthwise beams 124 run
generally parallel to the rails and generally transverse to the
cross beams. Lengthwise beams 124 need not have the features of the
cross beams. Of course, if the pallet is intended also for mounting
in racks which hold the pallet cross-wise, then beams 124 may have
the same features as are described for cross beams 126. In a pallet
having the desired cross beam features described herein, beams 124
may be displaced inwardly relative to the edges of the rails of the
rack, as for example, shown in FIG. 18 and FIG. 21. Because, in
this exemplary embodiment, the lengthwise beams are not
structurally attached to the cross beams, the engineered pallet
works even when both lengthwise beams lie vertically above the rack
rail when the pallet is stored.
[0068] Referring now to FIGS. 19-21, exemplary beam configurations
are illustrated. FIG. 19 illustrates an exemplary configuration
wherein beams 126 overlie one cross rail 30, but not another.
[0069] FIG. 20 illustrates an exemplary embodiment wherein cross
beams 126 are staggered in their offset. Beams 126A are offset to
the right, and beam 126B is offset to the left. So, in use two of
the beam ends at one side of the pallet have a gap G3 relative to
the rail 130L, while the other beam end has a gap G4 relative to
rail 130R.
[0070] FIG. 21 illustrates an exemplary embodiment wherein cross
beams 126 are all offset to one side of the pallet. That is, the
ends are farther from one side than from the other side. Thus, in
use all the beam ends will be farther from the rail 130L than from
rail 130R. Lengthwise beams 124 are also incorporated into the
pallet.
[0071] In certain exemplary embodiments, at least one cross beam
incorporates the features described. If a pallet has a beam which
fully spans the space between the opposing sides of the rack, when
one or more of the other beams are configured as described above,
in a fire, the pallet can be sufficiently weakened by the loss of
support of the short or offset beams, such that it will tip around
the one or more full length beams.
[0072] Referring now to FIG. 22, another exemplary embodiment,
incorporates a metal cross beam 126D made of two pieces joined by a
press-fit thermoplastic connector 132. In another exemplary
embodiment, the connector is offset from the center of the beam
length, so it is not under a column. In such embodiment, there will
be less mass of plastic to provide thermal inertia and inhibit
heating and softening during a fire. The plastic of the connector
may have the same or different properties, as compared to the
plastic of the pallet. When there is a fire, the plastic of the
connector 132 melts and fails, under the stresses imposed by the
pallet weight and whatever load is on the pallet, and the pallet
collapses. In this embodiment and the following two embodiments,
the lengths of the cross beams may be short or of regular
length.
[0073] As mentioned above, the beam need not be a metal material,
but may comprise other materials. In another exemplary embodiment,
a beam is made of composite plastic material, for instance a strong
fiber reinforcement, which beam in incorporated into a less strong
matrix or molding compound. The matrix is chosen so that it
deteriorates when heated, so that the reinforcing material can no
longer serve its purpose and the beam collapses. For example, the
beam may comprise long strand glass fibers or graphite fibers
contained in a thermoplastic matrix which may or may not be
different from the thermoplastic material of the pallet. The matrix
softens and yields when there is a fire. Thus, the fibers will be
no longer firmly gripped, relative to one another. The beam then
loses its structural modulus, its shape, and its load capacity, and
it and the pallet collapse. As an example, the reinforcement may be
glass or graphite or metal fiber and the matrix may be high density
polyethylene HDPE, polypropylene PP, polysufone PSF,
polyethersulfone PES, or analogous material
[0074] In another exemplary embodiment, the beam comprises
lamellae, such as strips of sheet metal or strands of wire. For
example, the cross section of FIG. 23 shows tubular beam 126F,
comprising shaped pieces of light metal angles 134, held together
using a thermoplastic or other heat degradable adhesive, or an
injected encapsulating layer, as suggested by the dashed line 136
in the Figure. In a fire, the adhesive fails and the beams fails.
While softening is the likely intentional failure mode of the
plastics and matrixes here, other modes of failure due to heating
may ensue.
[0075] In certain exemplary embodiments, the beam is described as
embedded in plastic. It should also be recognized that simply
placing the beam near such plastic may be sufficient, as long as
melting of the plastic causes the beam to fail or displace. For
example, suitable arrangements include placing the beam in a slot,
wherein the beam may be partially exposed. Particularly for those
embodiments which used a composite structure beam, there may be
openings or thinner sections in the plastic around the beam, to
speed localized heating and weakening of the beam during a
fire.
[0076] The principles of the invention may also be applied to other
products where there is a static load or dynamic load on the
product and the structure desirably loses its strength in event of
a fire or other thermal excursion.
[0077] In another exemplary aspect, 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] Referring now to FIG. 24, a vertical cross section through a
plane, just off the center of an exemplary pallet is illustrated.
As illustrated, the exemplary pallet 320 has a base 36 comprising
of cross rails having internal metal beams 326A, 326B, and columns
334 running up from the base (exemplary column 334 is illustrated
as positioned at an outer edge 324 of pallet 320), which support a
rectangular frame 338, having internal metal beam 326T. A
corrugated metal deck 322 is mounted in the frame 338. It should be
noted that exemplary components are shown in simplified and
conceptual manner. The beams 326A, 326B, 326T are contained within
solid plastic sections. In an exemplary embodiment, the structural
components also include hollows. More particularly, the outer
portion of the frame 338 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 330 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 332 in the frame may or may not be filled with
foam.
[0083] Referring now to FIG. 25, another simplified and exemplary
configuration of pallet 320A is illustrated, wherein the deck 322A
and columns (or feet) 334 are comprise hollow structural plastic. A
foam is provided within the hollow portions of the deck 322A and
columns 334. 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.
[0084] Any of the foam described herein may optionally include fire
retardants (it being understood that the presently described
structural components including faom 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 burn-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.
[0085] In one exemplary embodiment of the invention, a hollow
structure of HDPE or PE (for example the column 334 of FIG. 24),
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.
[0086] 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.
[0087] 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.
[0088] In another exemplary embodiment, a molded column 334 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.
[0089] Referring now to FIG. 26, another exemplary embodiment
illustrates a thermoplastic structural element comprising an I-beam
section 330 that is partially or fully covered with foam 342. 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.
[0090] 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.
[0091] Referring now to FIG. 27, an exemplary combination of
certain fire resistant features is illustrated. FIG. 27 shows a
40.times.48 inch pallet 420, to illustrate the exemplary features
of the invention. Pallet 420 has a rectangular base 422 and top
424. The base comprises peripheral rails 428 and cross rails 430. A
multiplicity of integral columns 436 (e.g., nine) run upwardly from
the base to support the top. There are steel beams 430 within the
rails. The columns have hollows 434 which are filled with
polyurethane thermoset foam. Top 424 is comprised of rectangular
plastic frame 434, which has selectively placed hollows or voids
436, e.g. in the spans between the columns. Metal deck 432,
preferably made of corrugated aluminum sheet with drain hole
perforations, is supported by and attached to the frame.
[0092] The top cooperates with the structure of the base and
columns, to provide requisite strength to the pallet. Since the top
is in good fraction aluminum sheet which does not burn readily in a
fire test, the amount of plastic in the pallet is reduced. The base
has metal beams which are configured for controlled collapse in a
fire. The columns have hollows as does the periphery of the frame
has voids or hollows. Those and the metal beams, as well as the
structural strength of the metal deck, cooperate to reduce the
amount of structural plastic in the pallet without compromising
structural performance. While thermoset foam burns, it burns at a
lower rate than structural thermoplastic. Since the amount of
plastic in the whole pallet is reduced, compared to a pallet
without the metal parts and without any interior hollows or foam,
the amount of heat release from a pallet during a test is reduced.
Since the pallet is light, it reduces the amount of thermoplastic
and or fire retardant in the pallet. Limiting the amount of fire
retardant in a pallet helps keeps the weight within limits and
helps costs.
[0093] The pallet of the present invention is by weight about 50-70
percent thermoplastic having flame retardant; and about 30-50
percent metal. In an exemplary polypropylene pallet, the total
weight is about 55 pounds, the aluminum deck weighs about 6 lb
(11-12%), and the steel reinforcing beams weigh about 12.5 lb
(23-25%).
[0094] In burn tests, a comparable dimensioned and structural
strength pallet, which metal beams, but which had neither the metal
deck nor drain holes nor thermoset foam of the present invention,
performed in a far inferior manner to the present invention, when
the thermoplastic and fire retardant were the same. Thus, that
demonstrates that for a comparable structural performance, the
invention features just mentioned enable the plastic to have fire
retardant. That enables better properties or less costly raw
materials of additives.
[0095] While exemplary embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. It is to be
understood that the present invention has been described by way of
illustration and not limitation.
* * * * *