Note: Descriptions are shown in the official language in which they were submitted.
HIGH STRENGTH BLOW-MOLDED STRUCTURE
RELATED APPLICATIONS
[0001] This application claims priority as a continuation-in-part of
copending U.S. patent
application serial number 15/975,915, filed May 10, 2018, titled HIGH STRENGTH
BLOW-
MOLDED STRUCTURE, which claims priority to U.S provisional patent application
serial
number 62/645,216, filed March 20, 2018, titled HIGH STRENGTH BLOW-MOLDED
STRUCTURE, copending U.S. design patent application serial number 29/640,679,
filed March
16, 2018, titled BLOW-MOLDED STRUCTURE, and copending U.S. design patent
application
serial number 29/640,977, filed March 19, 2018, titled BLOW-MOLDED STRUCTURE.
TECHNICAL FIELD
[0002] The disclosure relates to structures constructed from blow-molded
plastic and, in
particular, to high-strength, low-weight, blow-molded plastic structures.
BACKGROUND
[0003] Various items, such as tables, chairs, partitions, walls, and
sports equipment are
formed from plastic. In order to reduce the weight of the items, blow-molded
plastic is typically
used. A blow-molded plastic structure has outer walls that enclose an interior
hollow space. While
the hollow interior enables the structures to be light-weight, the hollow
interior of such blow-
molded items may also reduce the strength of the item so that the item is
unable to support a
relatively large amount of weight or force.
[0004] It is known that strengthening ribs made of metal or other durable
material may be
added to a blow-molded structure to increase the load-bearing strength of the
structure. However,
such strengthening ribs often significantly increase the weight of the
structure and may create
stress points in attachment locations that lead to mechanical failure of the
structure.
1
Date Recue/Date Received 2020-08-17
[0005] Strengthening ribs may also be integrally formed from plastic
during the blow-
molding process in order to increase the load-bearing capability of the blow-
molded structure.
Such ribs may extend over portions of the length and width of the structure to
provide load-bearing
support for the structure. However, the integrally formed ribs typically
require the use of thicker
walls that add weight to the structure, increase production time, and increase
the cost of producing
such structures. The ribs may also interfere with other components of the
structure, such as support
legs for a table-top made of the blow-molded structure.
[0006] In view of the foregoing, there continues to be a need for blow-
molded structures
having improved load-bearing capability and a simple light-weight
configuration.
SUMMARY
[0007] Accordingly, embodiments described herein provide a blow-molded
plastic
structure having a hollow interior portion formed during a blow-molding
process. The blow-
molded plastic structure includes a first outer portion and a second outer
portion that is spaced
apart from the first outer portion, wherein the hollow interior portion is
disposed between the first
and second outer portions. The structure includes a pattern of structural
stiffening features that are
integrally formed in the second outer portion. The pattern of structural
stiffening features includes
a plurality of multipodal (i.e., tripodal) depressions disposed in rows and
columns. As the term is
used herein, "tripodal" is an adjective form of tripod, and refers to a
structure having three support
features. "Multipodal" more broadly refers to structures having two or more
support features. The
pattern of structural stiffening features includes interspersed regions
disposed in rows and columns
between the tripodal depressions. Each interspersed region has a maximum
height between the
first and second outer portions. Each of the tripodal depressions extends into
the hollow interior
portion, and includes three indentations disposed adjacent the first outer
portion, and includes an
island spaced away from the first outer portion. The island has three sides,
each of which is
disposed adjacent one of the three indentations.
[0008] In some embodiments, the centerline spacing between each island in
each row of
tripodal depressions is greater than four times the maximum height of the
interspersed regions.
[0009] In some embodiments, the centerline spacing between each island in
each row of
tripodal depressions ranges from about 144 to about 176 millimeters, and in
other embodiments,
2
Date Recue/Date Received 2020-08-17
the centerline spacing between each island in each row of tripodal depressions
ranges from about
86 to about 106 millimeters.
[00010] In some embodiments, the centerline spacing between each island in
each column
of tripodal depressions is greater than four times the maximum height of the
interspersed regions.
[00011] In some embodiments, the centerline spacing between each island in
each column
of tripodal depressions ranges from about 144 to about 176 millimeters, and in
other embodiments,
the centerline spacing between each island in each column of tripodal
depressions ranges from
about 79 to about 97 millimeters.
[00012] In some embodiments, one of the three indentations in a first
tripodal depression in
a row of tripodal depressions is spaced apart from a nearest one of the three
indentations in a
second tripodal depression in an adjacent row of tripodal depressions by
greater than three times
the maximum height of the interspersed regions.
[00013] In some embodiments, one of the three indentations in a first
tripodal depression in
a column of tripodal depressions is spaced apart from a nearest one of the
three indentations in a
second tripodal depression in an adjacent column of tripodal depressions by
greater than three
times the maximum height of the interspersed regions.
[00014] In some embodiments, the maximum height of the interspersed
regions ranges from
about 29.7 to about 36.3 millimeters, and in other embodiments, the maximum
height of the
interspersed regions ranges from about 18.0 to about 22.0 millimeters.
[00015] In some embodiments, the central portions of the three-sided
islands are spaced
away from the first outer portion by a distance that is less than half of the
average distance between
the first outer portion and second outer portion.
[00016] In some embodiments, the central portion of each three-sided
island is spaced away
from the first outer portion by a distance that ranges from about 6.0 to 9.0
millimeters.
[00017] In some embodiments, the distance between the first outer portion
and the second
outer portion within each indentation ranges from about 5.0 to about 7.0
millimeters.
[00018] In some embodiments, the blow-molded plastic structure comprises a
portion of a
tabletop, a chair, a bench, or a structural panel.
3
Date Recue/Date Received 2020-08-17
[00019] The foreoing and other aspects, features and advantages of the
disclosed
embodiments will become more fully apparent from the following detailed
description of preferred
embodiments and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[00020] The appended drawings contain figures illustrating aspects of
preferred
embodiments of the disclosure and further clarifying advantages and features
of the disclosed
embodiments. It will be appreciated that the drawings depict only preferred
embodiments and are
not intended to limit the scope of the claims. Accordingly, the disclosed
embodiments are
described and explained with additional specificity and detail through the use
of the accompanying
drawings in which:
[00021] FIG. 1 is a partial perspective view of a second outer portion of
a blow-molded
plastic structure according to a first embodiment;
[00022] FIG. 2 is a partial plan view of the second outer portion of a
blow-molded plastic
structure according to the first embodiment;
[00023] FIGS. 3A, 3B, and 3C are partial cross-sectional perspective views
of a blow-
molded plastic structure according to the first embodiment;
[00024] FIG. 4 is a cross-sectional perspective view of a portion of a
tabletop containing a
blow-molded plastic structure according to first embodiment;
[00025] FIG. 5 is a plan view of a second outer portion of a tabletop
containing a blow-
molded plastic structure according to the first embodiment;
[00026] FIGS. 6 and 8 are perspective views, not to scale, of tables
containing a blow-
molded plastic structure according to the disclosure;
[00027] FIG. 7 is a perspective view, not to scale, of a panel containing
a blow-molded
plastic structure according to the disclosure;
[00028] FIG. 9 is a perspective view, not to scale, of a chair containing
a blow-molded
plastic structure according to the disclosure;
4
Date Recue/Date Received 2020-08-17
[00029] FIGS. 10A and 10B are cross-sectional perspective views of a blow-
molded plastic
structure according to a second embodiment;
[00030] FIG. 11 is a partial plan view of a second outer portion of a blow-
molded plastic
structure according to the second embodiment;
[00031] FIGS. 12A and 12B are partial plan views of the second outer
portion of a blow-
molded plastic structure according to a third embodiment;
[00032] FIGS. 12C and 12D are cross-sectional views of the blow-molded
plastic structure
according to the third embodiment;
[00033] FIGS. 13A and 13B are partial plan views of the second outer
portion of a blow-
molded plastic structure according to a fourth embodiment; and
[00034] FIG. 13C is a cross-sectional view of the blow-molded plastic
structure according
to the fourth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[00035] As set forth above, the disclosure is generally directed to blow-
molded structures
that have increased strength and light weight. While strength and weight are
important
considerations, it will be appreciated that the blow-molded structures
described herein may be
adapted for use with other structures that do not require increased strength
and light weight.
[00036] As used herein, the terms top and bottom, front and rear, right and
left, horizontal
and vertical, and row and column are intended to provide understanding with
regard to the figures
and are not intended to limit the orientation of the disclosed structures. The
blow-molded
structures described herein may be disposed in a variety of desired
positions¨including various
angles, sideways and even upside-down.
[00037] First Embodiment
[00038] With reference now to FIGS. 1 and 2, there is shown in perspective
and plan views,
a portion of a blow-molded plastic structure 10 according to a first
embodiment of the invenion.
The structure 10 includes a first outer portion 12, and a second outer portion
14 that is generally
spaced apart from the first outer portion 12. In some embodiments, the first
outer portion 12 is
generally planar. The first outer portion 12 and the second outer portion 14
enclose a hollow
Date Recue/Date Received 2020-08-17
interior portion 16 formed during the blow-molding process. Specifically, the
disclosure is directed
to a pattern of structural stiffening features that include tripodal
depressions 18 formed as part of
the second outer portion 14 of the structure 10, such as the pattern of
tripodal depressions 18 within
the dashed line box 20. Each depression 18 extends toward the first outer
portion 12 of the
structure. The depressions 18 are arranged in rows 22 and columns 24 in the
second outer portion
14 of the structure 10, and this pattern may be repeated over a substantial
portion of the second
outer portion 14 of the structure. As shown in FIGS. 4 and 5, the rows 22 and
columns 24 may be
arranged such that each tripodal depression 18 is closely adjacent to another
tripodal depression
18 in an adjacent row 22 and column 24 over a substantial portion of the
second outer portion 14.
[00039] Referring now to FIG. 2, a plan view of the second outer portion 14
of the first
embodiment of the structure 10 is shown. In the center of each depression 18
is a three-sided
island 26 space part from the first outer portion 12. Each depression 18 also
includes an indentation
adjacent to each side of the three sided island 26, shown as indentations 28a,
28b and 28c.
Accordingly, as shown, the indentations 28a-c and island 26 form the central
portion of the tripodal
depression 18 in the second outer portion 14 of the structure 10. In the first
embodiment, the
center-to-center spacing D5 between the indentations 28a-c within each
depression 18 ranges from
about 11 mm to about 14 mm, and is preferably 12.5 mm. A centerline of each
row 22a of tripodal
depressions 18 is spaced apart from an adacent row 22b by a distance D1 that
ranges from about
62.3 mm to about 68.8 mm, and is preferably 65.5 mm. Likewise, each column 24a
of tripodal
depressions 18 is spaced apart from an adjacent column 24b by a distance D2
that ranges from
about 65.5 mm to about 72.5 mm, and is preferably 69.0 mm. As shown, the
indentations 28a in
one row 22a are spaced from indentations 28b and 28c in an adjacent row 22b by
a distance D3
that ranges from about 47.9 mm to about 52.9 mm, and is preferably 50.4 mm.
The indentations
28b in column 24b are spaced from indentations 28c in column 24a by a distance
D4 that ranges
from about 53.3 mm to about 58.9 mm, and is preferably 56.1 mm.
[00040] Although a preferred embodiment includes three indentations 28a-28c
in each
depression 18 that form a tripodal depression structure, other embodiments may
include more than
three indentations. For example, one embodiment provides four indentations
arranged in a
rectangular layout within each depression 18, thereby forming a quadripedal
depression structure.
Multi-indentation depression structures are generally referred to herein as
multipedal depression
structures.
6
Date Recue/Date Received 2020-08-17
[00041] With reference to FIGS. 3A, 3B, and 3C, a partial perspective,
cross-sectional view
of the first embodiment of the plastic molded structure 10 is illustrated. As
shown, the structural
stiffening features include convex regions 30 of the second outer portion 14
that are disposed
between the depressions 18 and have a height H1 (distance from the first outer
portion 12) that
ranges from about 17.5 mm to about 19.3 mm, and is preferably 18.4 mm. The
radius R of
curvature ranges from about 22 mm to about 26 mm, and is preferably 24.0 mm.
[00042] As shown in FIG. 3B, within each indentation 28a-28c, the height
H2 between the
second outer portion 14 and the first outer portion 12 ranges from about 2.5
mm to about 3.3 mm,
and is preferably less than about 16% of the height Hl. In a preferred
embodiment, the height H2
is 2.9 mm. Also within each indentation 28a-28c, the second outer portion 14
may be spaced
apart from or may contact the first outer portion 12 of the blow-molded
plastic structure, depending
on the load placed on the structure 10. The three-sided islands in the
depressions 18 have a central
height H3 that is preferably more than about 37% of the height H1 and less
than about 2.4 times
the height H2. The height H3 may range from about 6.0 mm to about 7.5 mm, and
is preferably
6.9 mm. The total depth of the each indentation 28a-28c (H1 ¨ H2) and is
preferably at least about
84% of the height Hl.
[00043] Also shown in FIG. 3B, an angle r is formed between the first
outer portion 12 and
the second outer portion 14. In various embodiments, the angle r may range
from about 38 degrees
to about 55 degrees. In one preferred embodiment, the angle r is about 40.6
degrees.
[00044] This pattern of structural stiffening features, including the
convex regions 30 and
the depressions 18, provides improved strength to the blow molded plastic
structure 10 and reduces
the flexibility of the structure 10 under a load.
[00045] In order to provide the desired structural performance of the blow-
molded plastic
structure 10, the plastic material of the second outer portion 14 typically
has a material thickness
T2 ranging from about 2.06 mm to about 2.54 mm. In a preferred embodiment
depicted in FIG.
3C, the material thickness of the second outer portion 14 may vary across the
convex region 30.
Table 1 below provides three examples of material thicknesses at five points
within the convex
region 30. As listed in Table 1, the dimensions Ti, H1, H2, and H3 are
slightly different in each
example. As will be appreciated by those skilled in the art, the plastic
thicknesses T2 and Ti of
outer portions 14 and 12 may vary depending on the particular application for
the blow-molded
7
Date Recue/Date Received 2020-08-17
plastic structure 10. Accordingly, a relatively light-weight blow-molded
plastic structure 10 may
be provided by using the structural configuration described herein.
Example Ti T21 122 T23 T24 T25 H1 H2 H3
1 2.15 2.25 2.27 2.29
2.25 2.06 18.39 2.87 6.85
2 2.51 2.45 2.36 2.49
2.54 2.38 18.52 3.06 6.73
3 2.41 2.40 2.51 2.45
2.34 2.24 18.56 3.01 6.81
Table 1
[00046] Referring again to FIG. 2, the area occupied by each depression 18
may be
approximated by a triangle 32, and area occupied by each convex region 30 may
be approximated
by a triangle 34. The combined total areas of the triangles 32 range from
about 45% to about 55%
of the total surface area of the second outer portion 14. Likewise, the
combined total areas of the
triangles 34 range from about 55% to about 45% of the total surface area of
the second outer
portion 14. Accordingly, a ratio between the total surface area of the convex
regions 30 and the
total surface area of the depressions 18 ranges from about 0.82 to about 1.22.
Each of the three-
sided islands 26 may be approximated by a triangle 38 having a surface area
that is less than or
equal to about 4% of the surface area of the triangle 32.
[00047] As shown in FIGS. 4 and 5, the depressions 18 cover a substantial
portion of the
second outer portion 14 of the blow-molded plastic structure 10. Additionally,
while the
depressions 18 are shown and described as being located in the second outer
portion 14 of the
structure 10, the depressions 18 be formed in any desired portion of the
structure 10. The
depressions 18 may be spaced so that each depression 18 contacts an adjacent
depression in an
adjacent row 22 and adjacent column 24 thereof over a significant portion of
the second outer
portion 14.
[00048] While the tripodal depressions 18, convex regions 30, and three-
sided islands 26
provide increased load carrying characteristics for the blow-molded plastic
structure 10, the second
outer portion 14 may include additional structures that provide increased
resistance to the
flexibility of the structure 10. In some embodiments, the second outer portion
14 also includes
one or more beams 40 and 42 which may be integrally molded into the second
outer portion 14
8
Date Recue/Date Received 2020-08-17
and may surround an area 44 containing the tripodal depressions 18 as shown.
Additional
stiffening of the second outer portion 14 may be provided by a raised lip 46
that is also integrally
molded into the second outer portion 14 of the structure 10.
[00049] Advantageously, the relatively small distance between the
depressions 18 increases
the structural integrity and strength of the blow-molded structure 10, which
allows the thicknesses
Ti and T2 of the first and second outer portions 12 and 14 of the blow-molded
structure 10 to be
reduced. Accordingly, less plastic material may be used to construct the blow-
molded plastic
structures 10 because of the reduced thicknesses of the first and second outer
portions. Minimizing
the amount of plastic used to produce the structure 10 may reduce the cost of
the structure as well
as reduce cooling times and thus manufacturing times for the structures 10.
More rapid cooling of
the structure 10 enables the structure to be removed from the mold more
quickly. The size and
shape of the depressions 18 may also reduce the need for multiple beams 40 and
42 to reduce the
flexibility of the structure 10.
[00050] Non-limiting examples of items that may incorporate the blow-molded
structure 10
may include tables 48 and 50 (FIGS. 6 and 8), which may be foldable and/or
collapsible tables, a
partition wall 52 (FIG. 7) that may be used as a structural panel in a wall or
partition or other
portions of a building, a chair 54 (FIG. 9) that may use the blow-molded
plastic structure 10 as
part of a seat 56 and/or back support 58 thereof, and a bench (FIG. 10A).
[00051] Second Embodiment
[00052] Referring now to FIG. 11, a plan view of the second outer portion
14 of a second
embodiment of the structure 10 is shown. As in the first embodiment, in the
center of each
depression 18 is a three-sided island 26 space part from the first outer
portion 12. Each depression
18 also includes an indentation adjacent to each side of the three sided
island 26, shown as
indentations 28a, 28b and 28c. The indentations 28a-c and island 26 form the
central portion of
the tripodal depression 18. In the second embodiment, the center-to-center
spacing D5 between
the indentations 28a-c within each depression 18 ranges from about 16.2 mm to
about 19.8 mm.
In a preferred embodiment, the distance D5 is 18.0 mm. A centerline of each
row 22a of tripodal
depressions 18 is spaced apart from an adacent row 22b by a distance D1 that
ranges from about
61.0 mm to about 67.4 mm. In a preferred embodiment, the distance D1 is 64.2
mm. Likewise,
each column 24a of tripodal depressions 18 is spaced apart from an adjacent
column 24b by a
9
Date Recue/Date Received 2020-08-17
distance D2 that ranges from about 49.1 mm to about 54.3 mm. In a preferred
embodiment, the
distance D2 is 51.7 mm. As shown, the indentations 28a in one row 22a are
spaced from
indentations 28b and 28c in an adjacent row 22b by a distance D3 that ranges
from about 42.6 mm
to about 47.0 mm, and indentations 28b in column 24b are spaced from
indentations 28c in column
24a by a distance D4 that ranges from about 28.7 mm to about 31.7 mm. In a
preferred
embodiment, the distance D3 is 44.8 mm and the distance D4 is 30.2 mm.
[00053] With reference to FIGS. 10A and 10B, a partial perspective, cross-
sectional view
of the second embodiment of the plastic molded structure 10 is illustrated. As
shown, the structural
stiffening features include interspersed regions 30 of the second outer
portion 14 that are disposed
between the depressions 18 and have a height H1 (distance from the first outer
portion 12) that
ranges from about 16.0 mm to about 17.8 mm. In a preferred embodiment, the
height H1 is 16.9
mm.
[00054] As shown in FIG. 10B, within each indentation 18, the height H2
between the
second outer portion 14 and the first outer portion 12 ranges from about 3.6
mm to about 4.8 mm
and is preferably less than about 25% of the height Hl. In a preferred
embodiment, the height H2
is 4.2 mm. The three-sided islands in the depressions 18 have a central height
H3 that is preferably
more than about 49% of the height H1 and less than about two times the height
H2. The height
H3 may range from about 7.5 mm to about 8.9 mm. In a preferred embodiment, the
height H3 is
8.4 mm. The total depth of the each indentation 28 (H1 ¨ H2) and is preferably
at least about 75%
of the height H1.
[00055] Also shown in FIG. 10B, an angle r is formed between the first
outer portion 12
and the second outer portion 14. In various embodiments, the angle r may range
from about 38
degrees to about 55 degrees. In one preferred embodiment, the angle r is about
44.2 degrees.
[00056] In order to provide the desired structural performance of the blow-
molded plastic
structure 10, the plastic material of the second outer portion 14 typically
has a material thickness
T2 ranging from about 2.6 mm to about 3.3 mm. The plastic material of the
first outer portion
12 preferably has a material thickness Ti ranging from about 3.1 mm to about
3.8 mm. Table 2
below provides three examples of material thicknesses Ti and T2 and with
corresponding
variations in height dimensions H1, H2, and H3.
Date Recue/Date Received 2020-08-17
Example Ti T2 H1 H2 H3
1 3.78 3.34 16.81 4.22 8.24
2 3.58 3.04 16.87 4.18 8.35
3 3.07 2.62 16.88 4.07 8.45
Table 2
[00057] Third Embodiment
[00058] FIGS. 12A-12D depict a portion of a blow-molded plastic structure
10 according
to a third embodiment of the invenion. The structure 10 includes a generally
planar first outer
portion 12 as described in the other embodiments, and a second outer portion
14 that is generally
spaced apart from the first outer portion 12. The first and second outer
portions enclose a hollow
interior portion 16 formed during the blow-molding process. The third
embodiment includes a
pattern of structural stiffening features in the form of the tripodal
depressions 18 integrally formed
in the second outer portion 14 of the structure 10. Each depression 18 extends
toward the first
outer portion 12 of the structure. The depressions 18 are arranged in rows 22
and columns 24 in
the second outer portion 14, and this pattern may be repeated over a
substantial portion of the
second outer portion 14 of the structure. As shown in FIG. 12A, the rows 22
and columns 24 may
be arranged such that each tripodal depression 18 is closely adjacent to
another tripodal depression
18 in an adjacent row 22 and column 24 over a substantial portion of the
second outer portion 14.
[00059] In the third embodiment, all of the depressions 18 in each row are
rotationally
flipped by 180 degrees with respect to all of the depressions 18 in adjacent
rows. For example, in
FIG. 12A, all of the depressions 18 in row 22a are rotationally flipped by 180
degrees with respect
to all of the depressions 18 in row 22b. Also, all of the depressions 18 in
each column are
rotationally flipped by 180 degrees with respect to all of the depressions 18
in adjacent columns.
For example, all of the depressions 18 in column 24a are rotationally flipped
by 180 degrees with
respect to all of the depressions 18 in column 24b.
[00060] As shown in FIGS. 12B-12C, in the center of each depression 18 is
a three-sided
island 26 space part from the first outer portion 12. Each depression 18 also
includes an indentation
adjacent to each side of the three sided island 26, shown as indentations 28a,
28b and 28c.
Accordingly, as shown, the indentations 28a-c and island 26 form the central
portion of the tripodal
11
Date Recue/Date Received 2020-08-17
depression 18 in the second outer portion 14 of the structure 10. In the third
embodiment, the
center-to-center spacing D5 between the indentations 28a-c within each
depression 18 ranges from
about 11 mm to about 14 mm, and is preferably 12.5 nun. A centerline of each
row 22a of tripodal
depressions 18 is spaced apart from an adacent row 22b by a distance D6 that
ranges from about
49.5 mm to about 60.5 mm, and is preferably 55.0 mm. Likewise, each column 24a
of tripodal
depressions 18 is spaced apart from an adjacent column 24b by a distance D7
that ranges from
about 49.5 mm to about 60.5 mm, and is preferably 55.0 mm. The centerline
spacing between
adjacent depressions 18 in each row and between adjacent depressions 18 in
each column is about
99 mm to about 121 mm, and is preferably 110 mm. The diagonal centerline
spacing D8 is about
70 mm to about 86 mm, and is preferably 78 mm.
[00061] As shown in FIG. 12D, the structural stiffening features include
the interspersed
regions 30 of the second outer portion 14 that are disposed between the
depressions 18. The
interspersed regions 30 have a height H1 (distance from the first outer
portion 12 to the second
outer portion 14) that ranges from about 29.7 mm to about 36.3 mm, and is
preferably 33.0 mm.
Within each indentation 28a-28c, the height H2 between the second outer
portion 14 and the first
outer portion 12 ranges from about 5.0 mm to about 6.0 mm. In a preferred
embodiment, the
height H2 is 5.5 mm. The total depth of the each indentation 28a-28c (H1 ¨ H2)
and is preferably
at least about 83% of the height Hi. Also within each indentation 28a-28c, the
second outer
portion 14 may be spaced apart from or may contact the first outer portion 12
of the blow-molded
plastic structure, depending on the load placed on the structure 10. The three-
sided islands 26 in
the depressions 18 have a central height H3 that is preferably greater than
about 20% of the height
H1 and less than about 1.3 times the height H2. The height H3 may range from
about 6.0 mm to
about 7.5 mm, and is preferably 6.9 mm.
[00062] In the third embodiment, the plastic material thicknesses Ti and T2
range from
about 3.8 mm to about 4.0 mm. As will be appreciated by those skilled in the
art, the plastic
thicknesses Ti and T2 may vary depending on the particular application for the
blow-molded
plastic structure 10.
[00063] Fourth Embodiment
[00064] FIGS. 13A-12c depict a portion of a blow-molded plastic structure
10 according to
a fourth embodiment of the invenion. The structure 10 includes a generally
planar first outer
12
Date Recue/Date Received 2020-08-17
portion 12 as described in the other embodiments, and a second outer portion
14 that is generally
spaced apart from the first outer portion 12. The first and second outer
portions enclose a hollow
interior portion 16 formed during the blow-molding process. The fourth
embodiment includes a
pattern of structural stiffening features in the form of the tripodal
depressions 18 integrally formed
in the second outer portion 14 of the structure 10. Each depression 18 extends
toward the first
outer portion 12 of the structure. The depressions 18 are arranged in rows 22
and columns 24 in
the second outer portion 14, and this pattern may be repeated over a
substantial portion of the
second outer portion 14 of the structure. As shown in FIG. 13A, the rows 22
and columns 24 may
be arranged such that each tripodal depression 18 is closely adjacent to
another tripodal depression
18 in an adjacent row 22 and column 24 over a substantial portion of the
second outer portion 14.
[00065] As depicted in FIG. 13A, in the fourth embodiment, all of the
depressions 18 in row
22a are rotationally aligned in the same direction. The rotational alignments
of the depressions 18
in the adjacent row 22b alternate from one to the next by 180 degrees. All of
the depressions 18
in row 22c are rotationally aligned in the same direction, but they are
rotationally flipped by 180
degrees with respect to the corresponding depressions 18 in row 22a. All of
the depressions 18 in
row 22d are aligned in the same directions as the corresponding depressions 18
in row 22b. The
pattern repeats beginning at the row below row 22d.
[00066] With continued reference to FIG. 13A, all of the depressions 18 in
column 24a are
rotationally aligned in the same direction. The rotational alignments of the
depressions 18 in the
adjacent column 24b alternate from one to the next by 180 degrees. All of the
depressions 18 in
column 24c are rotationally aligned in the same direction, but they are
rotationally flipped by 180
degrees with respect to the corresponding depressions 18 in column 24a. All of
the depressions
18 in column 24d are aligned in the same directions as the corresponding
depressions 18 in column
24b. The pattern repeats beginning at the column to the right of column 24d.
[00067] As shown in FIGS. 13B-13C, in the center of each depression 18 is a
three-sided
island 26 space part from the first outer portion 12. Each depression 18 also
includes an indentation
adjacent to each side of the three sided island 26, shown as indentations 28a,
28b and 28c.
Accordingly, as shown, the indentations 28a-c and island 26 form the central
portion of the tripodal
depression 18 in the second outer portion 14 of the structure 10. In the
fourth embodiment, the
center-to-center spacing D5 between the indentations 28a-c within each
depression 18 ranges from
13
Date Recue/Date Received 2020-08-17
about 11 mm to about 14 mm, and is preferably 12.5 mm. A centerline of each
row 22a of tripodal
depressions 18 is spaced apart from an adacent row 22b by a distance D9 that
ranges from about
39.6 mm to about 48.4 mm, and is preferably 44.0 mm. Likewise, each column 24a
of tripodal
depressions 18 is spaced apart from an adjacent column 24b by a distance D10
that ranges from
about 43.2 mm to about 52.2 mm, and is preferably 48.0 mm. The centerline
spacing between
adjacent depressions 18 in each row is about 86 mm to about 106 mm, and is
preferably 96 mm.
The centerline spacing between adjacent depressions 18 in each column is about
79 mm to about
97 mm, and is preferably 88 mm. The diagonal centerline spacing Dll is about
58.6 mm to about
71.6 mm, and is preferably 65.1 mm.
[00068] As shown in FIG. 13C, the structural stiffening features include
the regions
interspersed 30 of the second outer portion 14 that are disposed between the
depressions 18. The
interspersed regions 30 have a height H1 (distance from the first outer
portion 12 to the second
outer portion 14) that ranges from about 18.0 mm to about 22.0 mm, and is
preferably 20.0 mm.
Within each indentation 28a-28c, the height H2 between the second outer
portion 14 and the first
outer portion 12 ranges from about 5.4 mm to about 6.6 mm. In a preferred
embodiment, the
height H2 is 6.0 mm. The total depth of the each indentation 28a-28c (H1 ¨ H2)
and is preferably
at least about 83% of the height Hi. Also within each indentation 28a-28c, the
second outer
portion 14 may be spaced apart from or may contact the first outer portion 12
of the blow-molded
plastic structure, depending on the load placed on the structure 10. The three-
sided islands 26 in
the depressions 18 have a central height H3 that is preferably greater than
20% of the height H1
and less than about 1.3 times the height H2. The height H3 may range from
about 7.2 mm to about
8.8 mm, and is preferably 8.0 mm.
[00069] In the fourth embodiment, the plastic material thicknesses Ti and
T2 range from
about 3.8 mm to about 4.0 mm.
[00070] Advantages Over Conventional Structures
[00071] Ease of Production. Because the edges of the depressions 18 have a
large radius of
curvature (R), the structure 10 can be more easily removed from the blow
molding machine.
[00072] Increased Strength. During the production, the quantity of plastic
material (such as
HDPE) provided to the mold must be adjusted to provide an optimum amount of
material for the
drawing of the depression structure 14 in the mold. The curved structure of
the depressions 18
14
Date Recue/Date Received 2020-08-17
described herein allows for higher quantities of the plasic material for the
entire structure 10,
thereby helping to ensure that the areas of the structure around the
depressions 18 will not be too
soft when drawn in the mold. In this way, adequate strength can be more evenly
maintained across
the top and bottom surfaces of the structure 10.
[00073] Reduced Defective Rate. Because of the large radius of curvature
(R) of the
depressions 18, the depth to which material is drawn in the mold is not as
deep as is typical of
conventional blow-molded structures. Thus, the drawing area of the bottom
surface of the
structure 10 will not be too soft, thereby significantly reducing the rate of
defects caused by low
strength in the bottom surface.
[00074] Better Performance. Because the depressions 18 are not as deep as
depressions in
conventional blow-molded structures, the bottom surface of the structure 10
can be thinner, which
requires less material. Less material in the bottom surface allows for more
material to be used in
the top surface without an overall increase in material per unit. This allows
for the top surface to
be made thicker, and therefore stronger and more durable, which results in
better physical
performance, such as in impact tests and loading tests.
[00075] Less Material Required for Production. Also because the depressions
18 are not as
deep as depressions in conventional blow-molded structures, less material per
unit is needed for
production of the structure 10, while maintaining at least the same strength
as conventional
structures.
[00076] Reduced Production Time. Because of the depression structure, the
wall thickness
over the entire structure 10 can be more even than is possible with
conventional blow-molded
structures. This allows production workers to be able to adjust and fine-tune
the operation of the
blow-mold machine for the structure 10 faster and more efficiently than was
possible with
conventional structures. This reduces the idle time for the machine.
[00077] Support of Three-Indentation Depressions. Because the depressions
18 having
three indentations 28a, 28b, 28c, can be more evenly distributed across the
bottom surface of the
structure 10, the material drawing rate in the mold can be reduced. Although a
four-indentation
(quadripedal) depression embodiment may provide greater strength overall,
quadripedal
depressions require a higher drawing rate, which requires more material per
unit for production.
Date Recue/Date Received 2020-08-17
Thus, from a material standpoint, the tripodal depressions 18 of the preferred
embodiment provide
an advantage over a four-indentation design.
[00078]
The present invention may be embodied in other specific forms without
departing
from its spirit or essential characteristics. The described embodiments are to
be considered in all
respects only as illustrative and not restrictive. The range and scope of the
disclosed embodiemnts
is, therefore, indicated by appended claims. All changes which come within
meaning and scope
of the appended claims are to be embraced within their scope.
16
Date Recue/Date Received 2020-08-17
