Note: Descriptions are shown in the official language in which they were submitted.
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BLOW MOLDED PALLET WITH WAVE-LIKE SUPPORTS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to the held of plastics. More
particularly, the
present invention relates to a pallet system and a pallet apparatus and a
method of pallet
manufacturing. Specifically, one preferred embodiment of the present invention
relates to blow
molding a first pallet section or portion with a wave-like support and then
inserting it into
another mold to j oin it to a second blow molded pallet section or portion
with a wave-like
support.
2. Discussion of the Related Art
Pallets are used for transporting and storing various types of cargo
throughout the
world. Therefore, it is important for a pallet to be lightweight, compact and
strong.
Traditionally pallets were made of wood, however, plastic pallets are now
being used with
increased frequency as they are lightweight, generally stronger, do not absorb
moisture, and they
can be cleaned and disinfected which is important in particular for the food
industry.
One disadvantage of plastic pallets is that they tend to break up with
continued use over time.
Therefore, for these and other various reasons it is important that plastic
pallets be reinforced by
a variety of means. . _ . . _ . .
The below-referenced U.S. patents disclose embodiments that were at least in
part
satisfactory for the purposes for which they were intended. The disclosure of
all the below-
referenced prior United States patents, in their entireties, are hereby
expressly incorporated by
reference into the present application for purposes including, but not limited
to, indicating the
background of the present invention and illustrating the state of the art.
U.S. Patent No. 5,417,167 discloses a plastic shipping pallet of the type
usually
manufactured from wood which is made of hollow plastic stringers and deck
boards. The
stringers and deck boards are made of plastic materials that may be either
virgin plastic, recycled
plastics or mixes. The stringers and deck boards are hollow but have closed
ends to prevent entry
of dirt, fluids, insects and vermin. The stringers and declc boards may be
made in a blow molding
process or using continuous extrusion and molding processes similar to that
used in the
manufacture of cornigated pipe. Various connection configurations for affixing
the deck boards
to the stringers are described including fixation by screws as well as
interlocking connections
between the plastic parts themselves and the use of separate interlocking
components that engage
the deck board and stringers.
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U.S. patent No. 5,845,588 discloses a pallet fabricated of a thermoplastic
material which
is produced by joining together individually fabricated structural components,
each of which is
individually thermoformed from an extruded plastic parison of a multiplayer
structure. The
structural components include a deck in the form of a continuous sheet with
longiW dinal and
transverse sides, one or more upper runner components fastened by their top
side to the bottom
of the deck, each of which includes a cross member with downward-facing posts,
and one or
more lower runner components, each of which includes a cross member with
upward-facing
posts and which is fastened by the tops of its posts to the bottoms of
matching posts on the
corresponding upper runner components.
U.S. patent No. 5,868,080 discloses a reinforced plastic pallet construction
and assembly
method are presented wherein multiple reinforcing bars are employed. At least
some of the
reinforcing bars have an exposed surface at a topside surface, underneath
surface or underside
surface of the pallet. In addition to functioning as a reinforcing member, the
exposed surfaces of
the reinforcing bars comprise an anti-skid surface for maintaining positioning
of payload on the
pallet or facilitating transport of the pallet, e.g., via a forklift or
automated transport system.
Various techniques for retaining the reinforcing bars within channels form in
the plastic pallet
body are described. The reinforcing bars preferably comprise composite strucW
ral members of
fiberglass-reinforced plastic fabricated from a pultrusion process.
U.S. Patent No. 6,209,464 discloses a pallet that includes a rectangular
support deck
having a substantially planar upper supporting surface including a plurality
of channels formed
therein and extending across the pallet. The deck includes support members
extending fiom an
underside of the deck that nest in recesses formed in the upper surface of the
deck. An alignment
portion is formed at a center point along the first edge of the deck and a
second alignment
portion is formed at a center point of an opposed edge of the deck. The
alignment portion
includes angled sides for receiving a tapered member of a complement device.
SUMMARY AND OBJECTS OF THE INVENTION
It is one object of the present invention to provide a pallet system that is
relatively
inexpensive to manufacture, recyclable, and environmentally friendly.
It is another object, to provide a pallet design that is structurally strong,
yet relatively
lightweight, and generally easy to manufacture.
In accordance with one aspect of the invention, the inventive pallet stem has
a first
portion and a second portion having interiors that fit together to provide
strength and stability to
a preferably blow molded pallet body.
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These and other aspects and objects of the present invention will be better
appreciated
and understood when considered in conjunction with the following description
and
accompanying drawings. It should be understood, however, that the following
description, while
indicating preferred embodiments of the present invention, is given by way of
illustration an not
of limitation. Many changes and modifications may be made within the scope of
the present
invention without 'departing from the spirit thereof, and the invention
includes all such
modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
A clear conception of the advantages and features constituting the present
invention, and
of the construction and operation of typical mechanisms provided with the
present invention,
will become more readily apparent by referring to the exemplary, and therefore
non-limiting,
embodiments illustrated in the drawings accompanying and forming a part of
this specification,
wherein like reference numerals designate the same elements in the several
views, and in which:
Fig. 1 shows a top perspective view of one embodiment of the pallet of the
present
invention;
Fig. 1A shows a cross-sectional view along line A-A in Fig. 1;
Fig. 1B shows a cross-sectional view along line B-B of Fig. l;
Fig. 1C shows a cross-sectional view along line C-C of Fig. 1;
Fig. 1D shows a cross-sectional view along line D-D of Fig.l;
Fig: 1E shows a cross-sectional view along line E-E of Fig. 1;
Fig. 2 shows a bottom-perspective view of the pallet of Fig. 1;
Fig. 3 shows an exploded top-perspective view of the pallet of Fig. l;
Fig. 4 shows an exploded bottom-perspective view of the pallet of Fig. 1;
Fig. 5 shows an exploded front view of the pallet of Fig. l;
Fig. 6 shows mold form halves used to form the pallet of Fig. 1;
Fig. 7 is a top-perspective view of another embodiment of the present
invention;
Fig. 8 is a bottom-perspective view of the pallet of Fig. 7;
Fig. 9 is a front view of the pallet of Fig. 7;
Fig. 10 s a side view of the pallet of Fig. 7;
Fig. 11 is an exploded top-perspective view of the pallet of Fig. 7;
Fig. 12 is an exploded bottom perspective view of the pallet of Fig. 7;
Fig. 13 is an exploded top-perspective view of yet still another embodiment of
the pallet
of the present invention;
Fig. 14 is an exploded bottom-perspective view of the pallet of Fig. 13;
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Fig. 15 is an exploded front view of the pallet of Fig. 13;
Fig. 16 is a side view of the pallet of Fig. 13; and
Fig. 17 is an exploded top-perspective view of yet still another embodiment of
the pallet
of the present invention;
Fig. 18 is an exploded bottom-perspective view of the pallet of Fig. 17;
Fig. 19 s sectional schematic with a magnified view of the pallet of Fig.l7;
Fig.20 is a side view of another embodiment of the present invention; and
Fig. 21 is a schematic illustrating the method of the present invention.
In describing the preferred embodiment of the invention, which is illustrated
in the
drawings, specific terminology will be resorted to for the sake of clarity.
However, it is not
intended that the invention be limited to the specific terms so selected and
it is to be understood
that each specific term includes all technical equivalents that operate in a
similar manner to
accomplish a similar purpose. For example, the word "connected" or teens
similar thereto are
often used. They are not limited to direct connection but include connection
through other
elements where such connection is recognized as being equivalent by those
skilled in the art.
DETAILED DESCRIPTION
The present invention and the various features and advantageous details
thereof are
explained more fully with reference to the non-limiting embodiments described
in detail in the
following description,
1. Resume
As shown in the embodiment of Fig. I, the present invention comprises a pallet
system
that has a body including a first portion and a second portion. The first
portion is preferably the
op portion and the second portion is preferably the bottom portion. The first
portion has a
generally planar outer surface and an inner surface at least a portion of
which is distant the outer
surface. The inner surface of the first portion is non-planar. In one
preferred embodiment
adjacent one set of outer edges, the imier surface has a pair of generally U-
shaped feet that
extend from one edge of the pallet to an opposing edge. Preferably, at the
bottom of each foot is
a rib that extends the length of the foot. Inside each foot and parallel to it
is a chamiel. Between
the channels and parallel to them is a middle support having generally the
same width as each
channel. The middle support extends away from the outer surface a distance
less than the
distance that the feet extend away from the outer surface.
The channels and middle support has a succession of curves having spaced apart
ridges
that define grooves.
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The second portion has an outer surface and an inner surface at least a
portion of which is
distant the outer surface. The inner surfaces of the first and second portions
each have
complementary undulating forms. The inner surfaces of the first and second
portions each
include a succession of curves.
5 The outer surface of the second portion includes at least a pair of channels
that extend
from one edge to an opposing edge. The pair of channels is dimensioned a
configured to receive
tines of a forklift. On each outer side of the tine-accepting channels is a
leg with at least one foot
at extends parallel to the channels from one edge to an opposing edge and that
rests on a surface.
In a preferred erribodiment, the feet run the longitudinal length of the
pallet. In between the pair
1'0 of channels is a support that extends parallel to the channels and
preferably spans the
longitudinal length of the pallet.
The inner surfaces of the ftrst and second portions each includes a succession
of curves
having rises and falls that run perpendicular to the series of ridges and
grooves on the outer
surface of the second portion.
The inner surface of the first portion is molded to the inner surface of the
second portion.
The outer surface of the second portion comprises a series of ridges and
grooves.
The outer surface of the ftrst portion is generally planar such that, e.g.,
boxes can be
stacked upon it.
The inner surface of the first portion is connected to the inner surface of
the second
portion. The inner surface of the ftrst portion and the inner surface of the
second portion
comprise complementarily shaped surfaces.
2. Presently Preferred Embodiments
With reference now to the drawing ftgures in which like reference numerals
designate
like parts throughout the disclosure, Fig. 1 sliows a pallet system 5 of the
present invention.
As best shown in Figs. lA-Fig. 4, the pallet system 5 consists of a pallet
body 10 having a ftrst or
upper portion 12 with a first outer surface 14 and a first inner surface 16
(see Fig. 4). The pallet
body also has a second or bottom portion 20 having a second outer surface 22
and a second inner
surface 24 (see, e.g., Figs. 2 and 3). A ftrst distant portion 18 is also
contained in the first
portion 12 and a second distant portion 26 is contained in the second portion
20 (see Fig. 1A).
The ftrst portion 12 preferably has a first set of protnisions 30 which
connect to the second
portion 20. In one preferred embodiment, protnisions 30 interdigitate between
a second set of
protrusions 32 1 ocated on the second portion 20 (see Fig. 3).
As best shown in Fig. 4, a first leg 38 and a second leg 39 may also be
provided on the
pallet body 10. In other embodiments, these legs acW ally may be made up of
one or more feet
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(40, 41, 42,43, 44, and 45) as shown in Figs. 7 through 12. As shown in yet
another embodiment
(Figs. 13-15), the legs 38, 39 are preferably formed from an extension 51 on
the first portion 12
that is received by a channel 46 on the second portion 20 as best shown in
Fig. 15.
In one embodiment, one significant feature is that a plurality of con-ugations
56a, 58a
from the first portion 12 preferably interconnect with a plurality of
corrugations 56b, 58b from
the second portion 20. The cornxgations may be made up of a combination of
humps 56 and
valleys 58 in combination with ridges 52 and grooves 48 (see, e.g., Figs. 4,
12 and 14). The
ridges, humps, valleys and grooves may have various shapes and sizes. When the
corrugations
are mated together, the upper corrugations 56a, 58a may have extending members
76 in the
middle between the tine holes which fit into cavities 78 in the tine holes on
the lower
corrugations 56b, 58b (see Fig. 14).
The corrugations may run along the X direction and/or the y direction.
Preferably, the Y
direction is 48-inches and the X direction is 40-inches.
As shown in Fig. 15, one preferred embodiment also has apertures 80 which
receive ribs
or locking members 82. Escape holes 84 may also be formed in the first portion
12 and the
second portion 20 by mold form pins (not shown) to allow the injected gases
that are inserted in
the blow molding process to properly escape. When the extending W embers 76
and the cavity 78
come together while the blow molded plastic portions are still hot, they may
form an attachment
or tack- off point 90 (see Figs. l, 7, 9).
As shown in Fig. 13, the embodiment may have inserts 94 that are formed from a
more
rubberized plastic (e.g., EVA). This material also has greater friction to
prevent loads from
slipping off an otherwise slick polyethylene top surface. Alternatively, a
coating 96 may be
applied as shown in Fig. 11 where it is shown applied to one half of the first
outer
surface 14.
In one embodiment, best shown in Fig. 16, the body 10 of the pallet system is
"bowed" at
an angle a from the horizontal plane. Angle a is preferably 6° or less.
2. Manufacture
The presently preferred embodiments are preferably manufactured in several
ways.
Fig. 17 shows a general process flow diagram illustrating the method used to
construct
the pallet of the present invention. The process begins preferably with the
first forming of the
bottom portion in a conventional blow molding form having two halves. The
cycle times and
molding characteristics are adjusted to the materials being molded. When
inserts are required
they may be molded in a separate injection molding process. The bottom portion
is formed to
mate with the mold form used to blow mold the top portion. Additional chemical
bond or bon-
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promoting agents may be used or some roughening of the surface may also be
used to enhance
bonding. A gap or air port may be provided between these pieces so that air
can be released
during the bonding of the two portions together. Such a gap normally occurs
around the midline
or pinch-off area where the mold halves meet.
Fig. 6 depicts one pair of symmetrical extrusion mold forms that are used to
form a pallet
portion. Water-cooling channels within the mold form (not shown), parison
pinch-offs
(not shown) and air/gas access ports or needles (not shown) are provided in
conventional
fashion within the mold form to effect proper molding. It may be necessary to
provide grooves,
clamps, or other retaining mechanisms within the mold to provide retention of
the lower piece
into the mold foim for the upper piece.
First, various types of plastic (e.g., virgin and recycled) are added to a
hopper. The
hopper feeds an extruder where the plastic is heated. A parison of molten
plastic (e.g., a
polyethylene material) is next extruded and vertically suspended between mold
halves.
Typically, the material is heated to a molten state and the temperature is in
the range from 350°F
to 450°F. One the material is introduced into the mold form, the
parison is pinched off as the
mold closes. After the mold closes about the parison, an air or gas is
injected via one or more
injection needles into the parison. The air is directed such that the material
is blown onto the
contoured wall surfaces of the mold forms.
The pallet portions may be made out of a variety of materials such as linear
low
Polyethylene (LLPE), high-density polyethylene (HDPE), and/or may include some
natural
rubber. For example, a mixture of 20% to 30% polyethylene and a natural rubber
product
called Duraprene may be used. This allows for a flexible yet strong pallet
which can
properly carry o three thousand pounds. One preferred material will the meet
the following
ASTM stand D297, D412, Die G, D624, Die C, F36, D2240, F147, D471,as well as
ASTM #1, #3, and Fuel A and Fuel C. Duraprene can be obtained through a
company called
Lamatelc (see htt ://www.lamatek.com .
Next, the bottom portion is placed into a mold form to make an upper portion.
Retaining pins or clamps may hold the bottom portion in the mold form. Parison
is again
extruded between the mold form halves and the above process begins again. The
blown
polyethylene material thereby retains the bottom portion against the mold
walls. During this
insert molding process, other already formed pieces (such as rings to add
surface friction) may
also be inserted into the blow mold form (having two halves) where they are
retained during the
blow molding process and integrally bonded into one of the newly formed blow-
molded
surfaces. Relative temperatures of the inserted pieces and/or bottom portion
and the material are
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such that the hot material coats and melts the inner surface of the pieces
and/or the portion to
coalesce and form integral bond with one another. Depending on the materials,
the mold forms
may also preheat and soften the pieces and/or portions. For the pieces, an EEA
material may be
used while polyethylene may be used for the portions.
The EEA material used has a melt temperature typically in the range of
250°F to 300°F
and the preferred polyethylene material typically has a melt temperature in
the range of 375° to
450°F. Other relative temperature ranges could be used, provided the
materials will flow melt
bond to one another. It is important that the dwell time of each mold is
properly set to prevent
the formation of air pockets at the bonding surface that can prevent proper
lamination.
Further increasing the cooling time may be necessary to prevent any sinking or
shrinking
of the bonding surface. Again, which could produce unwanted delamination.
Alternatively,
reducing the dwell time helps to release air which becomes trapped at the
bonding surface during
molding. Typical cycle times of lx to 2x at air gas pressures of 80 psi to 150
psi and dwell times
of 1y to 1.5y, where y and x are comparable values for non-composite pieces of
identical design.
While the pallet body 10 is preferably formed from two blow mold portions, it
is possible
the portions may be formed by injection molding, theimo-forming, or another
plastic molding
process.
The depths of any grooves or projections (e.g., Fig. 15 references 80, 82)
that are used to
enhance bonding can be adjusted to take into account shrinking and/or melting
that occurs at the
bonding of the surface. The projections may comprise annular or lateral ribs
or studs or
combinations thereof. Dovetail projections or studs with heads may also be
used. Some
projections may serve to retain a tread piece while others create an air
channel and melt away.
As shown in Figs. 13-16, the upper portion 12 may be made of a first plastic
mixture and
the bottom portion 20 may be made of a second plastic mixture. Such mixtures
may give the
give the upper and bottom portions different relative anti-slippage or weight-
bearing properties.
For example, the upper portion material (e.g., EEA and real rubber) may be
stiffer while the
bottom portion material may have greater impact strength.
The pre-formed insert pieces 94 are preferably constructed from a 1 ow
density, relatively
soft polyethylene material of the polyoleEn family. The material particularly
comprises an
ethylene-ethyl acrylate (EEA). This material doesn't readily bond to
polyethylene using
traditional adhesion methods, such as RF sealing, ultrasonic bonding or spin
welding. EEA,
however, is commercially available in a number of compositions that
accommodate a variety of
operating temperahmes or melt ranges below that of the materials used to blow
mold the pallet 5.
Two 18% EEA compositions having respective 20 and 6 melt ranges have been
shown to be
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desirable. The lower temperature (i.e. 20 melt) material is softer and
reeadily assures proper
bonding, but is less scuff resistant. Alternative pre-formed insert materials
may comprise ethyl-
vinyl acetate (EVA), low- density polyethylene (LDPE) or linear, low-density
polyethylene
(LLDPE). Variations of the foregoing materials may also be blended, as
necessary, to provide
desirable mechanical properties for particular application.
An EEA pre-formed insert material is presently preferred for the pallet 5
because it is
relatively durable and readily bonds under flow melt conditions to the
polyethylene upper
portion. The EA material is also less dense than many materials, in
particular, the polyethylene
materials used to typically mold the pallet. The pre-formed insert 94 thus
exhibits a softer
texture than the pallet top portion 12, which produces improved traction
between the pallet and
the load: Depending upon the application, it may however be desirable to use a
harder pre-
formed insert material, similar to that of the pallet top portion 12.
In the embodiments shown in Figs. 17-20, pallet 99 has a body 100. The runners
101
attached to the body 100 that are preferably designed with a slight radius
102, 103 on the outside
edges 104, 105 to add strength and durability and to prevent the pallet 99
from getting hung up
on expansion joints in a warehouse floor or a conveyor and also to prevent
breakage of fragile
comers or edges. In this embodiment, all of the pallet body's edges (e.g.,125)
have radiused
corners (see e.g, 106, 108, 110, 112, 114, and 116).
This palllet 99 may also have three components 118, 120, and 122 (a top,
middle and
bottom section respectively as shown in Figs 17 -19) or two components (e.g.,
a top and bottom
section as shown in Fig. 20) depending on the application. For example, the
three-portion pallet
would be used for more heavy-duty applications while the two-portion pallet
may be used for
medium-duty applications. The same molds may be used make the top sections and
bottom
sections of the three portion and two portion pallets. However, as can be
seen, a middle section
mold is only likely to be used by the three-portion heavy-duty pallet.
When the portions are insert molded, the portion weld points or tack or kiss-
offs 126
are preferably found at both the peaks 130 and the valleys 132 of the inner
aces 140, 141,
142, 143 where the portions 118, 120, and 122 meet as shown in Fig. 18. This
feature gives
added structural strength and stability to the pallet 99. Fig. 19 illustrates
this embodiment of the
blow-molded pallet 99 has a 0.5 inch lip 150 around the center edge 160. The
lip 150 allows for
easier handling by pallet transfer equipment and provides an anchor point for
plastic shrink-wrap
and/or tie down straps.
In the preferred embodiment shown in Figs. 17-19, the rumlers are preferably
about 4.75
inches high and about 6.5 inches wide. The peaks extend to a height about 0.75
inches from the
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inner surface and are about 1 inch wide. The pallet from top surface to bottom
surface is
approximately 5.75 inches high. The length of the pallet may be 40 inches and
the width may be
48 inches.
The runners or legs 101 are preferably formulated from a puncture resistant
HDPE plastic
5 resin. These HDPE plastics may be acquired from FORMOSA PLASTICS CORPORATION
USA (see www.fpcusa.com) and may, for example, include hexane copolymers,
homopolymers,
extra high molecular weight copolymers having densities between about 0.945 -
0.955 g/cc and
melt indexes about 0.30 -10.0 (HLMI) min. Alternatively, puncture resistant
properties may be
added by blending in plastics with these characteristics into the typical
polyethylene material.
10 Puncture resistance of the plastic is desirable in some applications
because some pallets are
frequently moved by forklifts bearing sharp tines or forks.
Of course, one of ordinary skilled may see other possible changes to the
pallet designs for
example with the corrugations running in the 40-inch direction. In the some of
the above
described embodiments, the corrugations in the bottom portion the pallet stop
at the inside face
of the runners, with the top surface (of the bottom portion) dropping into the
runners. However,
another design change (see, e.g., Figs. 17-19) involves rumiing the con-
ugations to the outside of
the runners, except at each end of the runner where the top surface will
continue to drop into the
runner. This change will help to stiffen the runners (rotationally), but still
provide an extra layer
at the ends of the runners that see impact from forks.
Adding additional structural rigidity may be accomplished by adding aluminum
or
steel inserts, running the length of the runners, in, for example, the four-
way pallet design.
The individual components described herein need not necessarily be formed in
the
disclosed shapes or assembled in the disclosed configuration, but could be
provided in virtually
any shape, and assembled in virtually any conftguration. Furthermore, all the
disclosed features
of each disclosed embodiment can be combined with, or substituted for, the
disclosed features of
every other disclosed embodiment except where such features are mutually
exclusive. Finally, it
is intended that the appended claims cover all such additions modiftcations
and rearrangements.
Expedient embodiments of the present invention are differentiated by the
appended claims.
What is claimed is:
