U.S. patent application number 11/358363 was filed with the patent office on 2006-09-14 for plastic pallet having deck suspension system.
Invention is credited to Ronald P. Brochu, Roy E. JR. Moore.
Application Number | 20060201400 11/358363 |
Document ID | / |
Family ID | 36969461 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060201400 |
Kind Code |
A1 |
Moore; Roy E. JR. ; et
al. |
September 14, 2006 |
Plastic pallet having deck suspension system
Abstract
The top of a thermoplastic pallet for transporting goods is
comprised of a frame which is mounted on columns extending upwardly
from a base. A subframe is attached to brackets within the interior
opening of the frame. The edges of corrugated metal deck is
attached to the subframe and spaced apart inwardly from the inner
edge of the frame. There are lengthwise spaces between the subframe
and the bridge parts of the frame, which bridges span the fork
opening spaces between the columns. When the bridges are
horizontally impacted, they can deform elastically into the spaces
without causing any damage to the deck. Preferably the bridges
comprise lengthwise impact absorber zones for good compliance to
horizontal impacts.
Inventors: |
Moore; Roy E. JR.;
(Killingworth, CT) ; Brochu; Ronald P.; (Richmond,
KY) |
Correspondence
Address: |
CHARLES G. NESSLER
P.O. BOX H
CHESTER
CT
06412
US
|
Family ID: |
36969461 |
Appl. No.: |
11/358363 |
Filed: |
February 21, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60654758 |
Feb 18, 2005 |
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60654760 |
Feb 18, 2005 |
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60654761 |
Feb 18, 2005 |
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60654766 |
Feb 18, 2005 |
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60654768 |
Feb 18, 2005 |
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Current U.S.
Class: |
108/57.25 |
Current CPC
Class: |
B65D 2519/00388
20130101; B65D 2519/00069 20130101; B65D 2519/00288 20130101; B65D
2519/00417 20130101; B65D 2519/00104 20130101; B65D 2519/00044
20130101; B65D 2519/00572 20130101; B65D 2519/00333 20130101; B65D
2519/00562 20130101; B65D 2519/00129 20130101; B65D 2519/00323
20130101; B65D 2519/00373 20130101; B65D 2519/00034 20130101; B65D
2519/00442 20130101; B65D 19/0059 20130101; B65D 2519/00407
20130101; B65D 2519/00024 20130101 |
Class at
Publication: |
108/057.25 |
International
Class: |
B65D 19/38 20060101
B65D019/38 |
Claims
1. A pallet comprising: a plurality of spaced apart columns; a
rectangular frame, attached to the tops of the columns and having
inner edges and outer edges, comprising a multiplicity of bridges
which span the spaces between the columns; a subframe, spaced apart
from the inside edges of the frame; means, adjacent the columns,
for supporting the subframe; and, a deck attached to the subframe;
wherein there are lengthwise spaces between the inside edge of each
bridge and the adjacent subframe.
2. The pallet of claim 1 further comprising a rectangular base,
wherein said columns extend upwardly from the periphery of the
base.
3. The pallet of claim 1 wherein the means for supporting the
subframe comprises a multiplicity of brackets attached to the inner
edge of the frame; and wherein each pair of adjacent brackets
bounds the ends of one of said lengthwise spaces.
4. The pallet of claim 1 wherein each space has a length which is
at least 75 percent of the length of the adjacent bridge.
5. The pallet of claim 4 wherein each space has a length which is
equal to the length of the associated bridge.
6. The pallet of claim 1 wherein each space has a length which is
at least 75 percent of the length of the adjacent bridge, wherein
each bridge further comprises at least one lengthwise impact
absorber zone.
7. The pallet of claim 6 wherein the pallet is composed
predominately of thermoplastic; and, wherein each bridge further
comprises a metal stay running along the length of at least one
bridge in proximity to the outer edge thereof.
8. The pallet of claim 1, further comprising: vertical ribs,
running transversely within at least one space, the ribs shaped for
low resistance to bending, to enable the bridge associated with the
space to deform inwardly under a horizontal impact load.
9. The pallet of claim 1 wherein a multiplicity of said spaces are
each at least one inch wide and 5 inches long, and sufficient in
shape to enable manual grasping of the pallet.
10. The pallet of claim 1 wherein the frame is comprised of
thermoplastic and the deck is a textured metal sheet.
11. The pallet of claim 10 wherein the deck has a circumscribing
flange where the deck is attached to the subframe.
12. The pallet of claim 1 wherein the deck is predominately
thermoplastic.
13. The pallet of claim 1 wherein the outer edges of the subframe
and of the deck are at least about 4 inches from the outside edge
of the frame.
14. The pallet of claim 1 wherein the edge of the deck extends
outwardly from the subframe over said spaces.
15. The pallet of claim 1 wherein the base is comprised of one or
more cross rails which run across the center of the base; wherein
the pallet further comprises a center column at the center of the
base; and, wherein the deck is attached to the top of the center
column.
16. The pallet of claim 3 wherein the subframe is an integral part
of the deck.
17. A rectangular pallet comprising: a base comprised of outer
rails interconnected to form a rectangle; eight spaced apart outer
columns extending upwardly from the outer rails and one center
column extending upwardly from the center of the base; a
rectangular frame, attached to the tops of the outer columns, the
frame having inner edges and outer edges and comprised of a
multiplicity of bridges which span the spaces between the columns;
a subframe, spaced apart from the inside edge of the frame; means
for supporting the subframe; and, a deck attached to the subframe,
the edges of the deck spaced apart from the inner edges of the
frame; wherein the deck and frame comprise the top of the
pallet.
18. The pallet of claim 16 wherein the means for supporting the
subframe comprises a plurality of brackets, one each extending
inwardly from the frame at the location of each outer column; and
wherein each pair of adjacent brackets bounds the ends of a space
running lengthwise between each bridge and adjacent portion of
subframe.
19. The pallet of claim 17 wherein each base rail comprises a metal
beam.
20. The pallet of claim 17 wherein the each bridge comprises an
impact absorber, and wherein the portions of the frame which
overlie the columns are free of impact absorber.
21. The pallet of 20 further comprising: metal stays proximate the
outside edges of each bridge; wherein the stay is closer to the
outer edge than is the impact absorber.
22. The pallet of claim 18 wherein the deck is fastened to the
subframe only at points between the columns and at the corner
column brackets.
23. In a rectangular predominately plastic pallet for use with a
forklift device, of the type having a top comprising a deck, where
the top is mounted on spaced apart columns which extend upwardly
from a pallet base, the improvement which comprises: a top
comprised of a rectangular frame which forms the periphery of the
top; the frame comprised of bridges which span spaces between the
columns; and a deck having edges which are spaced apart from the
inner edge of the frame along at least 75 percent of the length of
each bridge.
24. The pallet of claim 23 wherein the deck is connected to the
frame by means of brackets located in vicinity of the columns; and
wherein the bridges comprise length wise impact absorbers.
25. The pallet of claim 23 wherein the total of the lengths of all
spaces is greater than 50 percent of the length of the inner edge
of the frame.
Description
[0001] This application claims benefit of provisional patent
applications Ser. Nos. 60/654,758, 60/654,760, 60/654,761,
60/654,766, and 60/654,768, all filed Feb. 18, 2005.
TECHNICAL FIELD
[0002] The present invention relates to molded plastic pallets used
with forklift devices for transporting goods.
BACKGROUND OF THE INVENTION
[0003] A common wood or plastic pallet design, for carrying goods
with the use of fork lifting devices, has an essentially planar top
deck which is supported on columns or rails running upwardly from
the base. During use a pallet may be hit horizontally and damaged
by a hard object. For example, the tine of fork lift truck may hit
the edge of the pallet deck, or the pallet may be rammed against a
column or post. When common wood pallets are damaged in such ways,
a broken end slat can be removed and replaced However, many prior
art plastic pallets have had decks and other parts which are
integral, i.e., they are molded as one piece or are welded
together. When such kind of pallet is damaged, any repair can be
technically difficult and uneconomic. While pallets with detachable
parts are known, they tend to have a disadvantage in strength
compared to integrally molded or welded pallets.
[0004] Thus, to the extent possible, a plastic pallet should be
designed to resist damage, but not in a way which increases cost
and weight. That has been difficult to do. One approach involves
making the parts of a pallet more massive, or of a high performance
material. However, that can involve unacceptable increases in
weight, height, or cost.
[0005] In another approach, described in more detail in a related
patent application referred to below, the bridge part of a frame,
that part which spans the fork-opening space between adjacent
columns, is configured so it partially or wholly complies with the
load, that is, so it absorbs the force of the load by resiliently
deforming. However when the deck is attached to such a bridge part,
the deck can be buckled or torn loose, depending on how the bridge
is constructed and on the extent of the impact blow. The present
invention is also concerned with pallets having textured decks, for
instance corrugated metal decks. When such decks are deformed to
the extent of that pallet use is impaired, they have to be replaced
or the pallet may have to be discarded.
[0006] Thus, there is a need for improvement in the design of
pallets and in particular for enabling pallets to receive hard
horizontal blows, within the context of other restraints which
include having satisfactory structural strength, durability and
cost.
SUMMARY
[0007] An object of the invention is to provide a predominately
plastic pallet with resistance to impact damage. Another object is
to provide a means for attaching a deck to a pallet, particularly a
textured metal deck, in such a way that deformation of the deck is
avoided when the top edge of the pallet is hit and deformed by an
object. Another object is to facilitate manual handling plastic
pallets.
[0008] In accord with the invention, a predominately thermoplastic
pallet has a deck which is mounted on a subframe which is spaced
apart from the inside of the frame at the top of the pallet. The
pallet comprises a rectangular base, a plurality of spaced apart
columns extending upwardly, and a rectangular thermoplastic frame
mounted on the columns. The frame comprises a multiplicity of
bridges which span the spaces between the columns. The subframe is
supported within the interior of the frame, preferably by brackets
which cantilever inwardly from the frame in vicinity of the
columns. Each bridge preferably has an impact absorber, one or more
parallel zones of high compliance to horizontal impact load.
[0009] When impacted, such a bridge can deform inwardly into the
space adjacent the subframe while absorbing the blow, without
causing damage to the deck.
[0010] In a pallet embodiment in accord with the invention, the
space between each bridge and the subframe has a length which is
equal or less than the length of the bridge, and at least 75
percent of the length of the bridge. The space may be entirely open
and of dimension sufficient to enable a worker to insert a hand,
for manual movement of the pallet. In an alternate embodiment,
there is vertical ribbing within the space. It is shaped for high
compliance when the bridge deforms, and for insignificant load
transfer to the subframe when a bridge is horizontally
deformed.
[0011] The deck suspension system may be used with different kinds
of deck, including in a pallet having an all-plastic deck.
Preferably, the deck is made of diagonally corrugated metal and has
a peripheral flange. The deck flange is preferably attached to
subframe only at subframe locations which are adjacent the spaces
adjacent the bridges. In an alternate embodiment, the subframe may
be formed as an integral part of the deck.
[0012] The deck suspension system enables the use of bridges which
deform while absorbing impacts, and thus are durable. The foregoing
and other objects, features and advantages of the present invention
will become more apparent from the following description of
preferred embodiments and accompanying drawings.
[0013] The foregoing and other objects, features and advantages of
the present invention will become more apparent from the following
description of preferred embodiments and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an isometric partial cutaway top view of a
quadrant of a plastic pallet having a deck which is mounted on a
subframe suspension system.
[0015] FIG. 2 is a top view of a portion of the pallet of FIG. 1
with the deck removed.
[0016] FIG. 3 is a vertical cross section through the periphery of
the pallet of FIG. 1.
[0017] FIG. 4 is a top view of another embodiment of pallet.
[0018] FIG. 5 is a vertical cross section like FIG. 3, for an
alternative embodiment pallet.
[0019] FIG. 6 is an exploded view of a pallet like that shown in
FIG. 1.
DESCRIPTION
[0020] The invention is described in terms of a pallet which is in
the shape of a 40 inch.times.48 inch rectangle (1016 mm by 1219 mm)
and is called a GMA pallet. A comparable European pallet is a 1000
mm by 1200 mm pallet, sometimes called a CP-1 pallet. For such a
pallet to become accepted for widespread use in commerce, it must
meet various technical and performance standards. The Grocery
Manufacturers of America (GMA), Washington, D.C., U.S. in
conjunction with other organizations has published a document
entitled "Recommendations on the Grocery Industry Pallet System"
(1992). From that and other references, the current user-demanded
characteristics for an acceptable GMA pallet include the following:
The height must be less than 5.56 inches. The pallet must allow
four-way side entry by forks through side opening. The pallet
should weigh no more than 55 pounds, more preferably about 50
pounds. And the pallet has to meet a variety of structural
requirements. An exemplary pallet of the present invention meets
such requirements.
[0021] The pallets of the present invention may be molded in
components and subassemblies, preferably by injection molding using
gas assistance. See U.S. Pat. No. 5,401,459. The several parts or
subassemblies may be joined as an assembly by known thermoplastic
fabrication methods, for example, by mechanical means, by hot plate
welding, vibratory welding, or ultrasonic welding. See for
instance, U.S. Pat. Nos. 6,250,234 and 6,283,044. The thermoplastic
parts of the pallet may be made of commercial grade polypropylene,
high density polyethylene or other polyolefin. Other plastics,
including thermoset resins and engineered plastics, may be used for
the portions of the pallet.
[0022] FIG. 1 through 3 and the exploded view of FIG. 6 show pallet
20. The pallet comprises a frame 24 which is mounted on eight
columns 28 which run upwardly from the outside of the rectangular
pallet base 30, comprising corner columns and midpoint columns. In
this embodiment, the columns are molded integrally with the frame
and the top part of the base, but they may be separately formed.
Pallet base 30 is comprised of outer rails 31 which form a
rectangle which matches the shape of the frame. Cross rails 33
interconnect the centers of the outer rails and intersect at the
location of center column 29. In accord with Moore et al. U.S. Pat.
No. 6,705,237 patent, metal beams 74 run within the base rails 31,
33 for strength. The exploded view of FIG. 6 illustrates how the
beams may be inserted into cavities at the bottom of the molded
assembly, which are then closed by base cover plate 88.
[0023] Frame 24 is by definition a structure which circumscribes a
central space. A subframe 66 is positioned within the opening of
the frame 24. The subframe is analogous to the frame in defining a
central opening which is spanned by the deck. Subframe 66 has the
shape of an open center rectangle and is mounted on midpoint
brackets 68 and corner brackets 78. The combination of subframe and
brackets is referred to as the deck suspension system. Deck 22,
which is preferably made of textured sheet metal, for instance a
corrugated aluminum alloy, is attached to the subframe. Thus the
edge of the deck is spaced apart from the frame and the exterior of
the pallet. The deck, with such portions of the frame as are
exposed at the top of the pallet, provides the top surface of the
pallet, for carrying goods.
[0024] Openings 34, sometimes called windows, are spaces between
the columns through which forks are inserted for lifting. GMA
pallet openings must be least 3.1 inches high and 12 inches wide.
Bridges 25 are those portions of the frame 24 which span the
openings 34. In the invention, thermoplastic bridges 25 are
preferably constructed so that they resiliently deform in
compliance to the load, to thus distribute and absorb horizontal
impact forces. Upon removal of the impacting force, the bridge
resiliently resumes its original shape.
[0025] Compliance is the shape change of a bridge, responsive to an
applied force or load. For a given load, a bridge or portion
thereof which has high compliance will have greater deformation and
thus more gradual absorption of the force than will one which is
low in compliance. Generally, a structural member, such as the
subframe or the base is stiff and has low compliance. In the
invention, an impact absorber is a structure which has compliance
higher than a comparable size structure which is intended only for
structural purpose.
[0026] As can be seen in the exposed portions of the bridges shown
in FIG. 1 and FIG. 3, the impact absorbers 26 of bridges 25
comprise one or more lengthwise zones which have high compliance
compared to a solid structural member such as the subframe. The
impact absorber zones are preferably comprised of parallel rows of
closed cells 32 bounded by ribs 40 which run lengthwise and
transversely. In the embodiment shown, the cells 32 are smaller in
the lengthwise zone which is near the outer edge of the bridge than
they are in the zones which are near the inner edge 72 of the
bridge. Part or all of the cells may be open at the top and bottom.
Open cells 32B and 32A are shown in FIG. 4 and FIG. 5. The radii of
the interiors of the cells may be changed from large to small,
along with cell size, to further accomplish desired gradation in
internal compliance of the bridge across its width. A bridge may
have a metal stay which extends lengthwise proximate the outer
edge, to help impact resistance. The construction of impact
absorbing bridges, with and without stays, is described in the
patent application entitled "Plastic pallet having impact resisting
top", bearing Atty. No. EPC-2437, filed on even date herewith by D.
Swistak et al., the disclosure of which is hereby incorporated by
reference.
[0027] With reference to FIG. 1 and FIG. 3, the outer edges of the
subframe are spaced apart from the inner edges 72 of the frame.
Preferably, the brackets 68, 78 are integrally molded with the
frame and subframe, as shown. Other support means may be used,
including that the subframe may rest on the top of columns when
they wider than is shown here, or where the frame is narrower than
is shown. (In the exemplary pallets described here, a bracket may
be alternatively conceived as being part of the top of a column,
inasmuch the frame and column tops are integral in a finished
pallet.) In other variations of the invention, the subframe may be
comprised of multiple individual pieces rather than one rectangular
piece; the plastic subframe and brackets may include metal members
for strength; and, the subframe may be made of metal and may be
fastened to the brackets.
[0028] The outside of subframe 66 is spaced apart from the inner
edge 72 of the frame, and thus there is a space 30 adjacent each
bridge 25. The brackets bound the lengthwise ends of spaces 30.
Preferably, the brackets are shaped so that the ends of spaces 30
have rounded inside corners, to lessen stress concentration. The
spaces 30 enable inward deformation of a bridge under horizontal
impact, without consequential deformation of the subframe and
attached deck. Since the columns are sturdy, compared to the
bridges of the frame, the frame portions which run over the top of
the columns are much less prone to inward deformation when
impacted, although some motion may occur as indicated below.
[0029] A typical space 30 has a length which is equal to, or
somewhat less than, the length of the associated or adjacent
bridge. The length of each space 30 will be at least about 75
percent, preferably about 85 percent of the length of the
associated bridge. Spaces 30 may be centered relative to the bridge
or they may be off-center. See FIG. 2. The ends of a space 30 do
not extend beyond the ends of the bridges. As a corollary, the
bracket width is equal or greater than the associated column width.
Having a space 30 length which is less than the full length of the
bridge shortens the free span which is between the brackets, of the
associated subframe. That reduces the required section size of the
subframe portion, although there is some resultant increase in the
effective compliance of the bridge as a whole, since its free span
is also effectively diminished.
[0030] In an exemplary 40.times.48 pallet, a bridge is about 12
inches (30.5 cm) long, about 3 to 5 inches (7.5 to 12.7 cm) wide,
and about 0.7-0.8 inches (18 to 20 mm) high. The edge of the deck,
where it is attached to the subframe will be 4 to 5 inches (11 to
13 cm) or more spaced apart from the outer edge of the frame. The
associated adjacent subframe is about 1.5 inches (38 mm) wide and
0.7 inches (18 mm) thick. The space 30 will be about 10 inches
(25.4 cm) long. For an exemplary 40.times.48 pallet, when the deck
is inset about 5 inches (11 cm) the deck is 30 inch (76 cm) by 38
inch (97 cm) in dimension. Since the spaces 30 are at least 75
percent of the at least 12 inch (30 cm) length of the bridges, more
than fifty percent of the edge of the deck is not connected to the
bridge in a horizontal load transferring way; and when there are no
ribs in spaces 30 (as described below), the at least fifty percent
of the deck is not attached to anything.
[0031] Deck 22 preferably has the diagonal corrugations shown and a
flat circumscribing flange, where it attaches to the subframe. The
center of deck is attached to center column 29. Deck 22 is
preferably attached to the subframe in the following way: Fasteners
93 run through holes in the deck at carefully chosen locations. The
deck has a circumscribing flange 49 which is fastened to the
subframe at locations 73, that is, where the subframe runs between
the brackets and athwart the bridges. The deck is fixedly attached
to the subframe at the pinning locations 73 and thus is positively
located on the pallet. The deck is optionally also attached by its
corners to the subframe or to the brackets 78 at pinning locations
75, to prevent lifting and snagging of the corner during use. The
holes at locations 75 are preferably short length slotted holes,
running along the diagonal of the deck. They enable small movement
of the deck relative to its attachment under conditions of severe
impact. The midpoints of the deck edge are preferably not pinned to
the brackets 68. That enables a small impact-induced movement of
the frame, bracket and subframe at those midpoint column locations
under severe loads. In the generality of the invention the deck may
be attached to the subframe at any point along the length of the
deck edge, including in vicinity of the midpoint columns. The
fasteners for decks may be screws, rivets, or plastic pins which
extend upwardly from the subframe and which are headed after the
deck is set in place, as suggested in FIG. 1 and FIG. 3. Other
metal or plastic fasteners which are known may be used, within the
meaning of pinning. Within the meaning of attaching, adhesives may
be used.
[0032] The deck is preferably made of wrought aluminum alloy, such
as Type 5052 alloy. The outer edge 71 of deck flange 49 is slightly
down-turned into space 30, at the outside edge of the subframe.
That provides strength and avoids snagging of goods moved across
the pallet surface. See FIG. 3. In an alternate embodiment, the
edge of the deck may extend beyond the outer edge of the subframe
and overlie at least part of a space 30. For a further description
of the deck and variations, see the related application entitled
"Plastic pallet having metal deck", bearing Atty. No. EPC-2435,
filed on even date herewith by R. Brochu et al., the disclosure of
which is hereby incorporated by reference.
[0033] In the invention, the edge of the deck is inset, or spaced
apart inwardly from the outer edge of the frame, by a dimension
which is at least equal to the width of the frame and part of the
space. Thus, the deck will be protected from horizontal impact
blows on the side of the pallet. The spaces 30 between the bridges
and subframe are large enough to accommodate non-failing
deformation of the bridges, especially the large deformations which
can be associated with bridges having impact absorbers which
increase bridge compliance. For the exemplary pallet, the width of
an open space 30 between the inner edge of the bridge and the outer
edge of the subframe and associated deck is preferably about 0.5 to
1.5 inches (13 mm to 38 mm), most preferably about 1.3 inches (33
mm).
[0034] Preferably, spaces 30 have a length and width which is
sufficient to enable a worker to insert his or her hand, to
manually grasp and move the pallet. For such purposes, one or more
of the spaces 30 will be about 5 inches (12.7 cm) long and at least
one inch (2.5 cm) wide. The spaces also provide passages enabling
fire sprinkler water to fall onto the cross rails and any
underlying pallets or goods. Generally, the size of spaces may vary
with location around the top of the pallet.
[0035] While the spaces 30 are preferably devoid of any structure,
in other embodiments there can be structure within the spaces,
either to prevent objects from dropping through the spaces, or to
provide additional vertical load bearing structure for the top.
FIG. 4 is a top view of part of alternate embodiment pallet 20A. In
FIG. 4, and in FIG. 5 discussed next, numbers with suffixes denote
elements which correspond with those described above, except as
stated otherwise. In pallets 20A and 20B, a row of open cells
comprises impact absorber 32A, 32B in each bridge 25A, 25B. In FIG.
4, pallet 20A has spaces 30A which have the same lengths as their
associated bridges 25A, and the spaces contain a plurality of
vertical V-shape ribs 80. The ribs 80 are highly compliant to
horizontal load, since they readily bend or flex. Other
configuration ribs, such as curved ribs, which behave analogously,
can be used. Within pallet design limits, when the frame 25A is
deformed, ribs 80 flex and transfer load to the subframe which is
insubstantial in terms of causing the subframe and attached deck to
bend inwardly.
[0036] FIG. 5 shows in vertical cross section a portion of another
embodiment pallet 20A which has a different subframe construction.
The brackets 68B of the subframe are as previously described. Deck
22 is made of metal or plastic sheet and has a circumscribing
formed or rolled edge beam 52 in place of the previous described
flat flange. The edge beam 52 provides good section modulus and
beam strength to the deck edge, sufficient to support the deck
where it runs between the brackets. Thus, in this type of
embodiment the subframe is the edge beam 52. The subframe is
integral with the deck, rather than being integral with the
brackets. If the deck is a thick plastic structure, and it is
attached to brackets so its edge is spaced apart from the frame,
then the outer periphery of the deck will be considered the
subframe within the scope of present invention.
[0037] The deck suspension system of the present invention may be
used in pallets which have decks of still other constructions.
Plastic decks which are taught by the prior art may be used in
substitution of the preferred metal deck. For example, the deck may
be comprised of formed sheets, including extruded and pultruded
sheets, one or more perforated plates, a waffled construction, a
ribbed sheet, a metal-plastic composite, and so forth. A pallet of
the present invention may be entirely made of plastic, when GMA
requirements do not have to be met. A plastic deck may be welded
to, or may be formed integrally with, the plastic subframe, as
described. When deck is made of metal or non-metal sheet, the deck
may be plain although that will tend to increase weight, compared
to a textured sheet deck. A textured deck may have no flange and
may be directly attached to the subframe.
[0038] Most usually, all bridges in a pallet will have the same
construction, although they may vary. In the generality of the
present invention, bridges may be constructed in an ordinary manner
which is associated with plastic structural parts. That is, they
may lack impact absorbers. Even though not specially designed for
compliance, and not as good in sustaining repeated blows, such
bridges nonetheless may be sufficient in some applications
[0039] While the invention has been described in terms of the
familiar U.S. 40.times.48 pallet, it may be applied to smaller and
larger pallets, including pallets which do not have columns at
their side midpoints or base rails. The invention facilitates the
use of metal decks in thermoplastic pallets, which are described in
related applications, and enables the pallets to be stronger, lower
in height, and better in meeting fire test requirements than
heretofore was possible with predominately plastic pallets. The
deck suspensions system also enables better accommodation of such
thermal stresses as may arise during temperature changes,
particularly when the deck is metal.
[0040] Although this invention has been shown and described with
respect to one or more preferred embodiments, it will be understood
by those skilled in this art that various changes in form and
detail thereof may be made without departing from the spirit and
scope of the claimed invention.
* * * * *