Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates generally to one piece
plastic beverage bottles and more particularly to an improved
bottle of this type which has flat horizontal surfaces of
increased area that firmly support the bottle in an upright
position when filled.
A major difficulty with the use of plastic bottles
for carbonated beverages is the strength of the bottle base.
Due to internal carbonation pressures which can exceed 75 psi,
plastic bottles have a tendency to bulge outward at the base,
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resulting in what is referred to as a "rocker" which will rock
back and forth when standing on a flat surface or possibly tip
over. In addition, as the base bulges outward, the volume of
the bottle increases, thereby lowering the fill line such that
consumers may believe the bottIe was not properly filled or
sealed.
One solution to the problem of bulging is to provide
a bottle having a hemispherical base portion and attach
thereto a base cup having a flat lower surface for supporting
the bottle in an upright position. This type of bottle is
commonly referred to as a composite bottle. Composite bottles
are widely used for carbonated beverage bottles of sixteen
ounces or more. Increasing material cost for base cups has,
however, encouraged the development of one piece bottles
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having a self-supporting base whiah is reinforced to prevent
bulging due to carbonation pressures.
Several factors must be taken into consideration in
the evaluation of a bottle base. Stability is one of the most
important factors. A bottle must be stable when empty as well
as full. An empty bottle must be stable enough to stand
upright on bottle filling machinery. If bottles fall over
while being conveyed, the efficiency of the filling operation
will be adversely affected. To provide a stable bottle, the
diameter of the bottle engaging area which contacts a
supporting horizontal surface must be maximized. In addition,
the area of the base that is in surface-to-surface contact
with the supporting surface should be maximized.
Another evaluation factor is the strength of the
base in resisting bursting upon impact when the bottle is
filled. Stress cracking in the base will reduce the strength,
resulting in a base which bursts easily. The amount of stress
cracking is related to the base geome~ry. Relatively large
radius curves in the base will reduce the stress cracking
compared to a base with small radius curves.
Yet another~evaluation factor to consider is the
ability to properly vent the mold cavity when blow molding the
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~ bottle. Sufficient venting must be provided to ensure that
`~; the plastic material~will be blown completely into each leg of
the base to form feet at the lower ends of the legs which ~;
define the support surface engaging areas of the bottle.
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Several one piece bottles have been developed.
However, these bottles have one or more disadvantages
associated with their base structures. The base structure of
a plastic bottle will deflect downwardly when the bottle is
filled with a carbonated liquid. When this occurs in several
of the existing one piece bottles, the diameters and sizes of
the support surface engaging areas are decreased, resulting in
bottles of reduced stability when full.
Several prior bottles also have base geometries with
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small feet and relatively small radius curves. This results
in support instability and stress cracks which reduce the
strength of the base causing the base to burst upon impact.
With these short comings in the prior art in mind,
it is an object of this invention to provide a bottle with
flat support surface engaging areas of increased size and
increased diameter relative to the bottle diameter to thereby
improve stability of the filled bottle.
It is a further object of this invention to provide
a bottle wherein deflection of the base due to filling does
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not decrease the support surface engaging area. ~
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Accordingly it is a further object if the invention
to provide a container with larger radius bends and curves to
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reduce the possibilities for stress cracking.
SUMMARY OF THE INVENTION
The present invention provides a base structure for
a càrbonated beverage container with a tubular side wall. The
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base structure includes a bottom wall extending downwardly and
inwardly from the lower end of the tubular side wall. A
plurality of legs extend downwardly from the bottom wall and
terminate in planar feet havin~ radially inner and outer
edges. The outer edges of the feet form a non-continuous
support surface engaging area having a diameter only slightly
less than the diameter of the tubular side wall.
As a further improvement, the feet can be inclined
radially inward and upward so that when the container is
filled with a carbonated liquid, the pressure within the
container forces the feet to rotate generally about their
outer edges to substantially horizontal positions. In the
horizontal positions, the feet provide large
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surface-to-surface contact areas with the horizontal surface
on which the container is supported. When the container is
filled, the diameter of the support surface engaging areas of
the container is not reduced as it is in many prior art
containers when the containers are filled. When the container
is filled, the outer edges of the feet remain in contact with
the horizontal surface, providing support surface engaging
areas having a diameter equal to that of an empty container. ~-
The wall portions which extend downwardly from the
base bottom wall taper slightly inwardly from the container
tubular side wall. This taper is necessary to enable
manufacture of the container. By minimizing this taper as
much as possiblet the radial distance from the container axis
to the outer edges of the feet is maximized resulting in a
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relatively large diameter for the support surface engaging
areas. This improves the stability of the container. In
addition, a base with a larger diameter at its lower end
enables the planar surface area of the feet to be increased
over that shown in th~ prior art.
Furthermore, by increasing the diameter of the
support surface engaging area, the radius of curves within the ;~
base can be increased to reduce stress cracking in the base.
Further objects, features and advantages of the
invention will become apparent from a consideration of the
following description and the appended claims when taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS --~
Figure 1 is a sectional view of the base of a prior
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art container; -~
Figure 2 is a sectional view of the base of another
prior art container;
Figure 3 is a side elevational view of a container
of the present invention; ~;
Figure 4 is a bottom view of the container of Figure
3;
Figure 5 is a sectional view as seen from
substantially the line 5-5 of Figure 4;
Figure 5A is an enlarged view of a portion of Figure
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1 330959
Figure 6 is a side eleva~ional view o~ a modified
form of the container of this invention,
Figure 7 is a side elevational view of the container
of Figure 6 showing a different view of the base structure of
- the container from that shown in ]Figure 6;
Figure 8 is a top plan view of the container of
Figures 6 and 7;
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: Figure 9 is a bottom view of the container of -~
Figures 6 and 7; and . -
~` Figure 10 is a sectional view as seen from : :
substantially the line ~o-lo in Figure 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
~: Prior art plastie container bases are shown in ~ ~ :
,. . .
Figures 1 and 2. Base 102 of Figure 1 has a plurality of
horizontal feet 104. The outer edges of the feet 104,
indicated at 105, define the outer edges of the container
support surface engaging areas having a diamater D. A center
portion 106 closes the base between~the inner edges 107 of the
feet 104. The center portio~l;106 projects inwardly into the
container formlng a wall with a concave outer surface.
When the container having the base 102 is filled
with~a carbonated liquid, the pressure in the container forces
the base to deflect downward such that the center portion 106
moves to the position shown in phantom line at 108. This in
turn causes a rotation of the feet 104 generally about the1r
outer edges 105 into the phantom line position at 110. In
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this position, the container is now supported on support
surface engaging areas having a diameter d corresponding to
the inner edge of the feet 110. The diameter d is
significantly smaller that the dlameter D, thus the stability
of the container has been reduced upon filling of the
container. - --~
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A base from another prior art container is shown in
Fi~ure 2. The base 112 has horizontal feet 114 and ribs 116
extending from the inner edges 118 of feet 114 transversely to
the opposite side wall of the bottle and joining the side wall
at 120. The support surface engaging areas of the base 112
have a diameter extending to the outer edges 122 of the feet
114 when the contalner is empty. However, when the container
iQ filled with a carbonated beverage, the pressure in the
container deflects the base 112 downward such that the
previously straight ribs 116 are now bowed downward as shown
by phantom line 124. This results in a rotation of the feet
114 generally about thelr outer edges 122 into the position
shown in the phantom line at 126. In this position, the
diameter of the~support surface engaging areas of the base now
extends only to the inner edges 128 of the feet 126 in the
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deflected position, thus reducing the stability of the filled
container from that of the empty container.
The plastic container of this invention includes a
base in which, when the container is filled, the diameter of
the~ support surface engaging areas is not reduced. A plastic
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beverage container, indicated generally ak 130, having a base
structure of this invention is shown in Figure 3. The
container is blow molded from a biaxlally oriented saturated
polyester, preferably polyethylene terephtalate (PET) and
includes an integral tapered top portion 132 which includes a
flange 134 and threaded neck 136. Extending downward from the
tapered top portion 132 is a hollow body having a tubular side
wall 138. The side wall 138 is generally cylindrical having
an upright longitudinal axis 139 through the center thereof.
A base 140 extends downwardly from the lower end of the side
wall 138 and closes the bottom of ths container 130.
. The base 140 has a downwardly extending bottom wall
142, best viewed in cross section in Figure 5. Bottom wall
142 is curved radially inwardly from the lower end of the
tubular~side wall 138. As shown in Figure 5, the bottom wall
142 is of a constant radius curve having a radius greater than
the radius of the tubular side wall 138. A relatively small
radius:fillet section 144, is used to merge the upper end of
the bottom wall 142 to the lower end of the side wall 138.
The bottom wall 142 terminates at the lower end in a center
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:~ section 146 that is substantially centrally of the base 140 ~ ~
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and intersects the axis 139. The center section is generally
horizontal at the center of said base although it may be ~ -.
slightly concave or convex. ~:
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The bottom wall is interrupted by a plurality of
downwardly projecting wall portions defining hollow legs ~ ~
radially spaced from the center section 146 and extending :-~ :
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below the bottom wall 142. These wall portlons include leg
side wall portions 148 and leg outer wall portions 150 as
illustrated in Figure 3. Leg outer wall portions 150 form
radially outer surfaces o~ the hollow legs. As shown, in
Figures 3 and 5, the leg outer wall portions 150 are of a
constant radius curve curving radially inwardly in a downward
direction. Leg side wall portion~ 148 extend downwardly from
*he bottom wall and radially inwardly from the leg outer wall
portions. The legs terminate in feet 152. Figure 5A is an
enlarged view of the foot portion of Figure 10. Each foot 152
is planar and generally trapezoidal in shape (Figure 4) having
an outer edge 154 which is generally parallel with inner edge
156. The side edges 155 of feet 152 taper toward one another,
radially inwardIy. The bottom wall circumferentially between
the hollow legs forms inverted V-shaped ribs to separate the
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hollow legs.
Each foot 152 defines a planar surface which is
inclined radially inwardly and upwardly such that the outer
edge 154 of each foot is lower than the inner edge 156 of each
foot. The outer edges 154 of the feet are adjacent the lower
edges of the outer leg wall portions 150 and are merged
thereto by a relatively small radius fillet section 158. The
outer edges 154 of the feet 152 form support surface engaging
areas for the container 130 having a diameter only slightly
less than the diameter of the side wall 138. By locating the
outer edges of the feet radially outward as much as possible,
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the stability of the bottle is improved.
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When the container 130 i6 filled with a carbonated
beverage, the pressure within the container forces the center
section 146 to deflect downward to the position indicated in
Figure 5 in broken lines 160. As a result of this downward
motion of the center section ~L46, the feet 152 also move
downward, rotating generally about the outer edges 154 to a
horizontal position shown at 162. In this rotated position,
the feet are now in surface-to-surface contact with the
horizontal surface 163 upon which the container is supported.
The outer edge of the engaging surfaces remains at 154 such
that diameter of the support surface engaging areas is not
reduced as a result of the deflection of the of the center
section 146. Thus the stability of the bottle is not reduced
when the bottle is filled.
The angle 157 which the feet 152 are inclined from
the horizontal support surface 163 depends upon the size of
the container and the material wall thickness of the base.
:
These two factors will determine the amount of deflection of
the base caused by internal pressure. It has been found that
an angle of approximately 9 is sufficient for most two liter
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and sixteen ounce containers.
In addition to maintaining the stability of the base `~
when the base is deflected, the surface area contact of the -
feet 162 with the surface 163 reduces wobbling of the
container. An upright container, when bumped, will tend to
wobble back and forth if it is not bumped hard enough to tip ;
over. This wobble will eventually dampen out and the
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container will come to rest. When the feet 162 are in
surface-to-surface contact with a support surface, the
dampening of wobble is greater than when the bottle is empty
and supported along the outer edges 154 of inclined ~eet 152. ~- -
Another embodiment of this invention is illustrated
with the blow molded plastic container designated generally at
10 in Figures 6-10. The container 10 includes an integral
tapered top portion 13 having a flange 12 and a threaded neck
18. The container lo also has a hollow tubular side wall 14
and an integral base 16.
The base 16, as shown in Figure lo, includes a
bottom wall extending downwardly from the side wall 14 having
an upper portion 20 and a lower portion 30 which is arcuate
radially inwardly in a downward direction. The bottom wall
terminates in a center section 28 substantially centrally of
the base 16.
The bottom wall is interrupted by a plurality of
downwardly projecting wall portions defining hollow legs 26 ;
extending below the bottom wall. These wall portions include
leg side wall portions 32 and leg outer wall portiQns 33. Leg
outer wall portions 33 form radially outer surfaces of the
hollow legs 26. As shown in Figure 10, leg outer wall -~ -;
portions 33 uniformly taper radially inwardly in a downward
direction. The legs terminate in planar feet 25 (Figure 10)
which merge with the center section 28. Feet 25 are inclined
radially inwardly and upwardly as shown in the ~roken lines
indicating the position of the feet when the container is
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empty. The ~olid lin~s, showing the feet at 27, illustrate
the position of the feet when the container is Pilled with a
carbonated be~erage. When the container is filled, the feet
25 rotate generally about their outer edges 24 to the position
shown at 27 in which the feet are in surface-to-surface
contact with a horizontal surface 29.
In both embodiments of the invention, having the
feet spaced radially outwardly as much as possible enables the
feet to have relatlvely large planar surfaoes to form support
surface engaging areas. The leg outer wall portions taper or
curve inwardly in a downward direction to facilitate removal
of the container from a mold. This taper or curve is
minimized as much as possible so that the diameter of the
non-continuous support surface engaging area, formed by the
outer edges of the feet, is only slightly less than the
diameter of the tubular side wall of the container. In
addition, this spacing allows the radii of the curved portions
in the base to be relatively large when compared with many
prior art containers, thus reducing or eliminating the
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possibilities for stress cracking in the base. It has been
found for both two liter and sixteen ounce containars that
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five feet is optimal to provide larger feet and larger radii ~
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curved portions in the base.
The containers 10 and 130 are blow molded from an ;~
injection molded plastic preform in a conventional manner. `~
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~he preform is heated to the temperature at which it can be -
blow molded and then placed into a mold cavity having an
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1 330~5q
interior surface of the desired configuration of the
container. Pressurized air is introduced into the preform to
expand the preform outwardly into contact with the mold cavity
interior surface. The air within the cavity is exhausted
through vent openings in the lower end of the mold cavity to
enable the plastic to be completely blown into the feet
portions of the mold cavity base portion. These vent openings
are in the form of narrow slots in the mold cavity which forms
small but noticeable lines in the bottle surface indicated by
lines 172 in Figure 4, lines 34 in Figure 9 and lines 36 in
Figures 6 and 7.
The hollow legs are formed by blowing the plastic
material of the bottom wall downward from the bottom wall.
The legs terminate in substantially flat support surface
engaging areas which are ballooned out of the bottom wall.
The inclined engaging areas rotate by internal pressure in the
container to form coplanar areas for engagement with a
horizontal surface for supporting the container thereon.
The invention provides a one piece blow molded
plastic container which has a seIf supporting base. The base
has a bottom wall extending from the lower end of the side
wall of the container. A plurality of legs extend downward
from the bottom wall forming hollow legs with planar feet that
are inclined upwardly and inwardly from the outer edges of the
legs. When filled with a carbonated beverage, the internal
pressure in the container forces the bottom of the base
downward, rotating the feet into a horizontal position
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defining co-planar support surface engaging areas for
supporting the container. This deflection does not result in
a decrease in the diameter of the container support surface
engaging areas, thereby not decreasing the ~tability of the
container when filled. In addition, the container base is
formed with relatively large radius curved portions to reduce
the amount of stress cracking in the base, thereby increasing
the strength of the base and reducing the possibility of
bursting.
It is to be understood that the invention is not
limited to the exact construction or method illustrated and
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described above, but that various changes and modifications
may be made without departing from the spirit and scope of the
invention as defined in the following claims.
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