Oriented fiber reinforced monolithic plastic foam pallet

A new and improved unitary plastic foam four-way entry pallet (10) comprising: a top deck (11), with perforated apertures (12), buttressed by a plurality of elongated support runners (13) which are profiled to receive material handling equipment; the runners are joined to a plurality of bottom members (14), perpendicular to the plane of the support runners. All the components are monolithically cast, in a mold, utilizing rigid plastic foam reinforced with oriented strand fibers to form homogenous matrix (16), which has a seamless, smooth finish (15), provided by the use of self-skinning foams.

FIELD OF THE INVENTION 
The invention relates to pallets, and specifically to an improved unitary 
plastic foam pallet with four-way entry by material handling equipment. 
BACKGROUND OF THE INVENTION 
Pallets for the unitizing of articles for shipping and storage have been in 
commerce many years. The most common in use is the wooden pallet 
consisting of a series of slats resting on runners, notched at their sides 
to achieve entry from four directions, and usually including bottom boards 
for extra rigidity. These components are commonly fastened together with 
nails. The wood used in these pallets is often not kiln dried. Because of 
rough usage, and the shrinking of the wood in drying with age, the nails 
become loose; this often causes damage to the cargo, loss of rigidity and 
often collapse of the pallet. Wooden pallets often cause wound injuries 
because of splinters, and back injuries because of their weight. Even with 
repairs, wooden pallets eventually must be disposed of when their useful 
life is over. The disposal cost at a landfill often approaches the 
original cost of the pallet. Because wooden pallets cannot be sterilized 
against bacteria and fungus infestation easily, they cannot be used for 
the transport of certain commodities. 
Plastic pallets overcome many of the deficiencies of wood; however they 
must often be reinforced for the necessary load capacities, or of such 
weight as to reduce their practicality. There have been many ways to 
approach this problem. Many, such as U.S. Pat. No. 3,719,157, to Arcocha 
et al., and U.S. Pat. No. 5,050,506, to Fiedler, have encapsulated plastic 
foam within rigid shells. Others, such as U.S. Pat. No. 3,861,326, to 
Brown, have used a rigid plastic foam sandwiching a corrugated fiberboard. 
Fiedler, U.S. Pat. No. 5,042,397, incorporates a corrugated fiberglass 
sheet material within each component comprising the pallet. In all of the 
above patents, the components must be fastened together with adhesives or 
bonding to complete the manufacture of the pallet. Cerugeira, U.S. Pat. 
No. 4,966,083, laminates several different materials, including metallic 
wiring, rubber, and curable material in a single block, which is then hot 
molded or pressed. 
SUMMARY OF THE INVENTION 
This invention is a monolithically cast pallet of unitary construction, 
wherein the components of the platform, runners and bottom members are 
formed in a single mold at the same time. Four-way entry is incorporated 
into the design to facilitate the use of material handling equipment. 
Plastic foam and oriented strand fibers are injected into the mold 
simultaneously. The result is a complete pallet, which eliminates the 
necessity of further assembly of the components, fastening the components 
with adhesives or bonding, or other finishing operations. While others 
have claimed monolithic assembly of components, in reality, their systems 
depend on prior or further assembly of components to achieve a so-called 
composite monolithic construction. This invention is one that produces a 
completely finished product in one casting operation and is truly 
monolithic. The invention achieves the goals of lightness and strength in 
a novel and simpler manner than any prior art pallet construction. Its 
uniqueness is its monolithic casting process. 
The unitary pallet, using reaction injection molding plastic foams, such as 
polyurethane, or other plastic foams which do not use chemical means to 
achieve froth, results in a closed cell, self skinned product that does 
not require surface treatment to inhibit the penetration of moisture, 
solvents and microorganisms. It can be easily sterilized and is free of 
voids or crevices in which bacteria or fungi might proliferate. 
By adjusting the density of the foam and the amount and type of 
reinforcement in the matrix, pallets of various weight holding capacity 
and lightness can be achieved. This accommodates air freight shippers on 
one hand and closed loop shippers on the other, where one requires a 
lightweight one-way pallet and the other a more durable one, having the 
capacity to carry heavy loads. 
The support members at the bottom of the pallet add load-bearing 
capabilities by distributing the weight and are a desired feature of 
volume users, such as bottlers, who must pass their pallets on a conveyor 
system to unitize loads, warehouse users, such as wholesale grocers, whose 
loaded pallets must be placed on pallet racks, and shippers of products, 
such as rolled roofing material, who desire to stack loads without the use 
of bottom sheets. 
Further, an added feature is the aspect of recycleability. Rejected 
assemblies and returned pallets from users can be ground up and used in 
the manufacture of new pallets. This can be as an additive granular 
ingredient, if the recycled pallet is of thermoset plastic materials, or 
as a plastic ingredient, in the case of thermoplastic materials.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a pallet 10 having a top deck 11 which is perforated with 
openings 12 for weight reduction and passage of air. The pallet deck is 
buttressed by elongated runners 13, these runners 13 are formed integrally 
with the top deck 11 and create walls. The runners 13 are notched to allow 
a fork lift to enter perpendicular to the runner 13. The bottom of the 
runners 13 are joined to bottom supports 14 which run perpendicular to the 
runners 13. FIG. 2 shows a bottom view of the pallet of FIG. 1 showing the 
bottom supports 14. The perforated openings have been eliminated from the 
upper deck in this view for clarity. 
FIG. 3 is a cutaway portion of a pallet showing the monolithic properties 
of the pallet, which are achieved without further fastening by mechanical 
or adhesive means. The elongated runners are of such dimension and are 
profiled in the mold, to receive the prongs of a forklift truck, pallet 
jack or other material handling equipment. The pallet is monolithically 
formed by casting or reaction injection molding plastic foam and oriented 
strand fibers simultaneously in a mold, under pressure, producing a 
homogenous matrix of uniform density and strength 16. The mold is 
constructed to achieve the triaxial openings to allow 4-way entry into the 
finished pallet, weight reduction, and air passage apertures in the pallet 
deck. The use of self-skinning plastic foams produces a smooth, seamless 
exterior surface 15 on all parts of the pallet in contact with the mold. 
The matrix can be easily adjusted for varying weight carrying capacities 
of the pallet by adjusting the density of the plastic foam and/or the 
quantity injected by the dispensing equipment, at the injection site and 
by adjusting the amount and the length of the oriented strand fibers 
included in the mixture. 
FIG. 4 is an isometric view of an alternative construction of the pallet. 
Upright pillars or legs 17 are used rather than elongated runners to 
support the upper deck. These legs 17 are located such that the openings 
(the same as the notches in the runners 13) for the fork lift are still 
present. The bottom supports 14 would interconnect all pillars. 
FIG. 5 is a schematic view of oriented fibers 18 oriented along their long 
axes by introduction into an enclosed airstream. Components that form 
rigid structural plastic foam, 19 and 20 are mixed by impingement and 
combined with the oriented fibers 18 to form a mixture 21 just prior to 
injection into a mold which forms the self-skinning outer skin 15 and 
matrix 16 of the monolithic pallet 10. 
FIG. 6 is a schematic of the plastic foam impregnated mixture 2 1 entering 
a gate valve of the mold to align the oriented fibers 18 along the long 
axes of the pallet runners 13. 
FIG. 7 is a schematic of the plastic foam impregnated mixture 2 1 entering 
gate valves of the mold to align the oriented fibers 18 along the long 
axes of the top platform 11 and bottom supports 14. The gate valves are 
located at opposing ends of the mold and are perpendicular to the flow of 
the mixture 21 as shown in FIG. 6. 
Reaction Injection Molding, with the acronym, RIM, process involves the 
high-pressure impingement mixing of two or more reactive liquid components 
and injection of the mixture into a closed mold at low pressures. The 
process is also called Liquid Injection Molding, High Pressure Impingement 
Molding and Reaction Liquid Impingement Molding, with the acronyms, LIM 
and RLIM. In this process, the two components of a resin such as urethane 
or other polymer are metered carefully and mixed at a very high pressure 
in a mixing chamber prior to injection into the mold where fast thermoset 
cure is achieved. Large and thick parts can be molded using fast cycles 
with relatively low-cost materials. Its low energy requirements with 
relatively low investment costs make RIM attractive. The low cost of RIM 
molding machines is the result of the low pressures that are used. 
When chopped-glass-fiber-reinforcement is added to the mixture, high values 
of modulus of elasticity and heat resistance are achieved. RIM generally 
delivers faster cycles than other processes with its high-pressure 
dispensing equipment to handle fast-acting resin systems. 
Reactive foams, such as polyurethane, in varying density formulation, are 
available worldwide from many chemical manufacturers. The equipment to 
dispense these chemicals is also widespread. Such equipment also has the 
capacity to include the dispensing of other desirous elements of the 
pallet composition, such as fire retardants, blowing agents, colorants and 
catalysts. This invention's conception is that such additives are not to 
be precluded from its patent. Nor is the scope of the invention limited to 
the use of plastic foams that are reactive solely by chemical means, but 
rather to include other plastics which may obtain their foaming properties 
by other means, such as inclusion of inert gases. 
The oriented strands, included for reinforcement, are also readily 
available. While the invention lends itself to the use of oriented glass 
filaments, commonly known as fiberglass, and sold by many manufacturers, 
such as Owens-Corning, it does not preclude the use of other organic and 
nonorganic fibers. Other fibers that could be used for reinforcing the 
pallet construction include, but are not limited to, Kevlar fibers, carbon 
fibers, polyester fibers, cellulose fibers, ceramic fibers, or metal 
fibers. The reinforcing fibers can be added as short chopped strands of 
0.10-0.25 inches or long strands of 0.75-1.00 inches to the plastic matrix 
material in the foamed or unfoamed condition, depending on the mixing and 
molding processes utilized; however, by orienting the fibers in a 
unidirectional path along the long axes of the various components greater 
strength is achieved. The longer fiber strands provide additional overlap 
between the oriented fiber strands within the foamed plastic matrix, 
lending greater strength and rigidity to the molded pallet. 
As shown in FIG. 6 and FIG. 7, the mold 30 into which the blended plastic 
foam and oriented fiber strands 21 is injected is a clam-shell design mold 
with removable cores 32 for maintaining the open spaces between the top 
platform 11, the bottom supports 14 and the runners 13 of the pallet. The 
mold is suitable for reaction injection molding or monolithic casting of 
the pallet. 
The manufacturing process, which is shown as a flow chart in FIG. 8 in a 
schematic diagram in FIG. 9 is as follows: 
1. An open mold 30, held in position on a mold carrier, is positioned at 
the site of injection of plastic foam ingredients and oriented strand 
fibers 21, simultaneously and in sufficient quantities to accomplish the 
requisites of density and strength. The fibers 18 are oriented by 
injecting them into an enclosed stream of air prior to contact with the 
plastic resin components 19 and 20, as shown in FIG. 5. The fibers 18 thus 
align themselves along their long axes by the airstream's pressure and 
flow. 
2. The chopped fibers 18 of sufficient length to achieve maximum overlap 
and plastic resin 19 and 20 are combined just prior to entrance into the 
mold 30, and simultaneously injected from three different directions into 
the mold 30. The blended resin 21 injected through the first injection 
port 34 orients the fiber strands along the long axis of the pallet 
runners 13, as shown in FIG. 6. Simultaneously, the blended resin 21 is 
also injected through two opposing injection ports 36 and 38, oriented 
perpendicular to the first injection port 34. The flow of the resin 21 
within the mold 30 orients the fiber strands 18 along the long axes of the 
top platform 11 and the bottom supports 14 of the pallet, as shown in FIG. 
7. The resin impregnated fibers 18 are thus aligned with a large 
percentage configured in a uni-directional, but perpendicular fashion, 
giving maximum strength along the long axis of each component of the 
pallet 10. 
3. The mold 30 is closed and is conveyed along the manufacturing line to 
cure while another mold is positioned at the injecting site. 
4. At a timed interval, which allows for curing of the matrix, the mold 30 
is opened and the completed monolithic pallet 10, comprising all the 
properties claimed, including triaxial intersecting openings, is removed. 
5. Optionally, an elastomeric coating can then be applied by spraying or 
dipping the completely formed monolithic pallet 10. Such a coating would 
contain materials to increase the pallet's impact and wear resistance. 
Such ready-to-apply materials could also impart other desired qualities 
including color, fire resistance or abrasive resistance. 
This invention is not to be limited by the embodiment shown in the drawings 
and described herein. The system has other far reaching applications in 
similar fields.