Squeezable container resistant to denting

A squeezable container with a paneled side wall which resists permanent deformation or denting when squeezed, and which preferably can be hot-filled. The container can be made substantially thinner than known hot-fill containers and includes a stepped vacuum panel profile for greater flexibility and resilience (bounce back). A circumferential ring is provided in the side wall to prevent ovalizing. The post walls (surrounding the vacuum panels) are stiffened to prevent vacuum collapse, by providing a substantially perpendicular junction between the vacuum panel and post wall, sufficient post wall depth, and/or reinforcing ribs in the post walls.

The present invention relates to a squeezable container which exhibits 
"bounce back" to resist permanent deformation or denting, and in a 
preferred embodiment to a squeezable, dent resistant container which can 
withstand hot filling without substantial deformation. 
Squeezable beverage containers are popular with bicycle riders and other 
athletes. These containers are typically made of polyethylene and may be 
squeezed between the fingers of one hand to dispense a liquid out a nozzle 
on the open top end of the container. However, the known polyethylene 
containers do not have the required thermal stability for receiving 
hot-fill (e.g., juice) products directly, and thus the squeezable 
container is typically sold separately from the beverage and the user then 
fills the container. It would be convenient if athletes and others could 
buy hot filled containers of juice as an "off-the shelf" item, which was 
both ready to-use and allowed repeated squeezable dispensing without 
permanent deformation. 
Hot-fill containers are adapted for the packaging of liquids (e.g., juice, 
beer) and other food products (e.g., jam) which must be placed in the 
container while hot to provide for adequate sterilization. During filling, 
the container is subjected to elevated temperatures (i.e., the product 
temperature) and positive internal pressures (i.e., the filling line 
pressure). For example, a juice container may be exposed to a product 
temperature on the order of 180.degree.-185.degree. F. 
(82.degree.-85.degree. C.) and a filling line pressure on the order of 2-5 
psi (30-75 atm). These temperatures and pressures may cause the container 
body to creep and/or shrink. An originally cylindrical container may 
"ovalize," i.e., increase in diameter in a nonuniform manner, especially 
in a tapered shoulder section between the neck finish and panel section. 
Containers with excessive shape distortion or ovalizing cause improper cap 
and label applications, and uneven or inadequate vacuum panel movement. 
A biaxially-oriented polyethylene terephthalate (PET) beverage bottle 
designed to receive a hot fill product with a minimum of thermal shrinkage 
and distortion is described in U.S. Pat. No. 4,863,046 entitled "Hot Fill 
Container," which issued Sep. 5, 1989 to Collette et al., and is hereby 
incorporated by reference in its entirety. The Collette et al. container 
was designed as a relatively large volume (32 or 64 ounces) beverage 
container. It has six symmetrically-disposed vacuum panels in the side 
wall of the container. The vacuum panels (all of them) deform and move 
radially inwardly in unison as the product cools in order to reduce the 
magnitude of the vacuum generated in the filled and capped container and 
to prevent any large uncontrolled shape distortion of the container. A 
wrap around label covers the vacuum panels and is supported by post walls 
surrounding the vacuum panels and a central panel wall in each panel. 
Vertical recessed ribs may be provided in the post walls to increase the 
longitudinal stiffness of the panel section. 
The design of the vacuum panels may vary; two other designs are illustrated 
in: 1) U.S. Design Pat. No. 315,869 entitled "Container Body For Liquids 
Or The Like," which issued Apr. 2, 1991 to Collette; and 2) copending and 
commonly-owned U.S. patent Ser. No. 07/792,449 entitled "Modular Mold," 
which was filed Nov. 15, 1991 by Collette et al., each of which is hereby 
incorporated by reference in its entirety. 
However, the previously described hot fill containers were designed for 
pouring, not squeezing. In fact, these typically large diameter bottles 
would permanently deform inwardly (buckle) if a user tried to push 
inwardly on the sidewall of the container to dispense the product by 
squeezing. Thus, the known PET hot fill containers have not been used as 
squeezable containers. 
It is an object of the present invention to provide a squeezable plastic 
container with panels that resists permanent deformation or denting. More 
preferably, it is an object of this invention to provide a squeezable 
container which is hot fillable. 
Summary of the Invention 
The container of this invention is squeezable, without undergoing permanent 
deformation or denting, and preferably is able to receive a hot fill 
product without undergoing excessive shape distortion. The container 
includes flexible vertically elongated panels in the side wall of the 
container, and stiffer post walls around the panels. The panels include a 
recess around a raised central panel wall and a connecting wall between 
the recess and panel wall is stepped to provide resilience. The flexible 
panels bow inwardly when squeezed and readily return (bounce back) to 
their original position and shape when released. 
Stiffening of the post walls around the panels is preferably achieved by 
providing substantially perpendicular junctions between the post wall and 
panel and by providing sufficient post depth (i.e., radial distance 
between the panel recess and post wall). In a preferred hot-fill 
embodiment, the stiff post walls prevent vacuum collapse of the container, 
while the multiple flex points and thin wall of the vacuum panels insure 
adequate movement under vacuum and enhance the flexibility and resilience 
(to prevent denting) of the panel section. 
It is preferable to provide a recessed circumferential ring in the side 
wall of the container to further minimize any shape distortion caused by 
filling with a hot product. This ring prevents a cylindrical container 
from ovalizing, especially in the tapered shoulder section of the 
container. 
Still further, vertically elongated ribs may be provided in the post wall 
to further stiffen the side wall against vacuum collapse. 
In a specific embodiment, a squeezable hot-fill container comprises a 
hollow plastic body having a resilient cylindrical side wall with a 
plurality of symmetrical vacuum panels aligned along a vertical 
centerline, an open upper end, and a closed bottom wall. The side wall 
includes symmetrically-arranged post walls disposed a first distance 
D.sub.1 from the vertical centerline. The vacuum panels are disposed 
between the post walls and each vacuum panel includes a vertically 
elongated recess surrounding a raised central panel wall. The recess has a 
lowermost flex point which is disposed a second distance D.sub.2 from the 
vertical centerline which is less than the first distance D.sub.1 of the 
post wall. The central panel is disposed radially outwardly from the 
lowermost flex point and a first connecting wall between the lowermost 
flex point and panel wall is stepped to provide flexibility and 
resilience. Preferably, a second connecting wall between the lowermost 
flex point and post wall is also stepped. The preferred container is a 
blow molded biaxially-oriented container made of a thermoplastic resin, 
and in particular a polyester such as a homopolymer or copolymer of 
polyethylene terephthalate, and preferably the panel section has an 
average wall thickness on the order of about 0.015" (0.38 mm) to about 
0.020" (0.51 mm). In a preferred small diameter (i.e., no more than about 
four inch) size container adapted to be squeezed in one hand, the average 
panel wall thickness is about 0.015 inches (0.38 mm) to about 0.017 inches 
(0.44 mm). 
Further details of the invention are more specifically described by the 
following drawings and description of certain preferred embodiments.

DETAILED DESCRIPTION 
A sectional panel view of a comparative PET hot-fill container is shown in 
FIG. 7. This comparative panel does not utilize the stepped wall 
construction of the present invention and undergoes permanent deformation 
when squeezed. 
The comparative container of FIG. 7 has a side wall 201 with a vacuum panel 
202 shown between a pair of post walls 208. The vacuum panel in its 
original (prior to squeezing) form is shown in solid lines as panel 202, 
and after squeezing in dashed lines as panel 203 which has undergone 
permanent deformation or denting. The panel includes a recess 204 having 
an outer connecting wall 205 adjacent the post wall 208 and an inner 
connecting wall 206 adjacent the raised central panel wall 207. The panel 
geometry and typical hot-fill wall thickness T' (e.g., 0.022 inches (0.56 
mm)) create a stiff panel which "locks up" and remains permanently 
deformed when it passes over the dashed center line 209. Thus, although 
this comparative container may have the necessary thermal stability and 
vacuum resistance for use with hot-fill products, it cannot be used as a 
squeezable container because it undergoes permanent deformation when 
squeezed. 
In accordance with this invention, a preferred hot-fill squeezable 
container 10 is provided as shown in FIG. 3. In this specific embodiment, 
the container is a 20-ounce, substantially transparent biaxially oriented 
PET beverage container which is about 7.87 inches (200 mm) in height 
(without the cap) and about 2.83 inches (72 mm) in outer diameter (at the 
panel section). The panel section 22 has been biaxially oriented and 
partially crystallized by being axially stretched and radially expanded in 
a blow mold, and has an average wall thickness of about 0.016 inches (0.41 
mm). This is considerably thinner than the prior known hot-fill containers 
which have had a wall thickness of about 0.022 inches (0.56 mm) to 0.024 
inches (0.62 mm). 
As illustrated in FIGS. 1-2, the container 10 is blow molded from a 
cylindrical injection-molded preform 2 having an open top end 11 and neck 
finish 12. The preform has a tapered shoulder-forming portion 5, 
substantially uniform thickness panel forming portion 3, and a 
base-forming portion 4 including a substantially hemispherical bottom end. 
The preform 2 is amorphous and substantially transparent and preferably is 
made from a PET monomer or copolymer (e.g., up to about 6% copolymer). 
However, other materials and preform shapes can be used, including 
preforms with thickened base forming portions to provide a thicker 
container base having improved creep resistance, or preforms with variable 
wall thickness portions in the side wall if desired. 
As shown in FIG. 2, the preform 2 is placed in a blow molding apparatus 96 
having an upper mold section 96A which engages the neck finish 12, a 
middle mold section 96B having an interior cavity forming the shape of the 
container side wall, and a lower mold section 96C having an upper surface 
forming the outwardly concave dome portion of the container base. In 
accordance with a standard reheat stretch blow mold process, the 
injection-molded preform 2 is first reheated to a temperature suitable for 
stretching and orientation, placed in the blow mold, and an axial stretch 
rod 97 is then inserted into the open upper end 11 and moved downwardly to 
axially stretch the preform. Subsequently or simultaneously an expansion 
gas 90 is introduced into the interior of the preform to radially expand 
the shoulder, sidewall and base forming portions outwardly into contact 
with the interior surfaces of mold sections 96B and 96C. 
As shown in FIGS. 2-3, the blown container has the same neck finish 12 with 
outer threads 13 and lowermost neck flange 14 as the preform. The 
remainder of the bottle has undergone expansion, although to varying 
degrees. An upper tapered shoulder portion 16 gradually increases in 
diameter and orientation while moving downwardly along the bottle. Next, a 
radially recessed circumferential ring 18 is provided between the shoulder 
section 16 and panel section 22 to prevent ovalizing. Below the ring 18 is 
a radially outwardly projecting upper bumper portion 20, and then a 
slightly recessed cylindrical panel section 22. Below the panel section is 
a radially outwardly projecting lower bumper 24, and then a 
champagne-style base 26. The base includes an outer base wall 28 gradually 
reducing in diameter moving downwardly from the upper bumper 24 to a 
lowermost contact radius 30 on which the bottle rests. Radially inwardly 
of the contact radius is a recessed inner base wall 32 or dome having a 
central gate region 34. The inner base wall or dome 32 may include a 
number of symmetrical recessed petaloid portions for increasing the 
thermal resistance of the base, as is known in the art. In general, the 
relatively low oriented base has a greater thickness for strength, while 
the panel section 22 has a relatively high orientation for strength. 
The cylindrical panel section 22 includes six equally sized and 
symmetrically arranged recessed vacuum panels 50 disposed about a vertical 
centerline 8. Surrounding each vacuum panel are post walls 40, which 
include upper post wall 41, lower post wall 42, and median post wall 43. A 
label (not shown) is wrapped around panel section 22 and lies in 
substantially smooth contact with all portions 41, 42, 43 of the post 
wall, and may be adhesively attached to upper and lower post walls 41, 42. 
As shown in FIG. 3, a removable cap 92 is attached to the open upper end of 
the container. The cap includes a base portion 95 having internal threads 
which engage the outer threads 13 on neck finish 12. At the upper end of 
the cap 92 is a sliding nozzle shown in a lowermost closed position 93 and 
an uppermost open position 94 (in dashed lines). When the panel section 22 
of the container is squeezed between the user's fingers (see opposing 
force lines 91 in FIG. 3), the panel deflects inwardly (see dashed panel 
lines 23) and the liquid product in the container is pushed out the open 
upper nozzle 94 by the internal pressure generated by squeezing. 
FIG. 4 shows in cross section the circumferential ring 18 disposed between 
the shoulder section 16 and upper bumper 20. The container side wall 
(outermost circumference) is disposed at a radial distance R.sub.1 from 
the vertical centerline 8. The ring 18 is recessed inwardly at a distance 
d.sub.1 from the outermost circumference. The ring 18 has a lowermost 
recess 19 of radius r.sub.1, outwardly expanding sidewall portions 21 
which define an angle .theta., and radiused junctions with the outermost 
circumference defined by radius r.sub.2. The specific dimensions, 
including the angular extent .theta., depth (d.sub.1), and values of 
radiuses r.sub.1 and r.sub.2, are determined by the specific geometry and 
resin properties of the container. Preferably the ring depth is about 
0.10R.sub.1 to about 0.24R.sub.1 (where R.sub.1 is the radius of the 
container) and the angular extent .theta. is about 45.degree. to about 
90.degree.. The lowermost recess preferably has a radius r.sub.1 of about 
0.3d.sub.1 to about 0.7d.sub.1 and the connecting radius r.sub.2 is at 
least about 0.3d.sub.1. 
As shown in FIG. 5, there are six symmetrical vacuum panels 50 disposed 
about the vertical centerline 8 of the container. FIG. 6 shows one of the 
vacuum panels 50, having a wall thickness T, and the manner in which it 
temporarily deforms when squeezed (dashed lines 23) and then returns to 
its substantially original undeformed position. The vacuum panel 50 lies 
between a pair of post walls 40 which are disposed at a distance D.sub.1 
from the vertical centerline 8. The post walls 40 are at the greatest 
distance from the centerline of any portion of the panel section 22 
(however, upper and lower bumpers 20 and 24 extend slightly outwardly from 
the panel section 22 to protect the label which is wrapped around the 
panel section). 
Each post wall 40 has an angular extent 2B and each vacuum panel 50 has an 
angular extent 2F, such that the total combined angular extents of all 
post walls and vacuum panels, i.e., 6(2F+2B)=360.degree. (the total panel 
circumference). Because there are six equal vacuum panels, the allowable 
angular extent 2A for each vacuum panel and its associated post wall is 
60.degree. (i.e., 360.degree..div.6=60.degree.). Preferably, each post 
wall has an angular extent 2B of about 12.degree. to about 21.degree. and 
each vacuum panel has an angular extent 2F of about 39.degree. to about 
48.degree.. 
Each vacuum panel 50 includes a vertically elongated recess 52 with a 
lowermost flex point 53 at a distance D.sub.2 from vertical centerline 8, 
which is less than the distance D.sub.1 of post wall 40. The recess 52 
surrounds a raised central panel wall 51, which is at a greater distance 
from the vertical centerline 8 than the distance D.sub.2. Preferably, each 
panel wall 51 has an angular extent 2C of about 12.degree. to about 
30.degree.. Preferably, the ratio of the panel height H (FIG. 3) to width 
(circumference) to insure ease of squeezability is at least about 2:1. 
Recess 52 has a lowermost flex point 53 and intermediate stepped connecting 
walls joining the flex point 53 with central raised wall 51 and post wall 
40. As best shown in FIG. 6, in going from lowermost flex point 53 to 
panel wall 51, there is a first connecting wall 58 having a first step 54, 
a second step 55, and a third step 56 disposed at radially increasing 
distances from the vertical centerline 8. In going from lowermost flex 
point 53 to post wall 40, there is a second connecting wall 60 having a 
first step 63 and second step 64 at radially increasing distances from the 
vertical centerline 8. These stepped walls form nine flex points, 
designated as 66, 67, 68, 69, 70, 71, 72, 73 and 74, and which, together 
with the thin panel wall, render the vacuum panels very flexible and 
resilient. The average panel wall thickness is preferably about 0.015 
inches (0.28 mm) to about 0.020 inches (0.51 mm). The "average" thickness 
includes the central panel 51 and first and second connecting walls 58 and 
60. Typically, the entire circumference of the side wall is of fairly 
uniform thickness, when a uniform thickness preform is used. However, in 
some cases it may be desirable to provide a thicker post wall 40 (e.g., by 
providing a variable thickness preform) for greater stiffness. Still 
further, the connecting walls 58, 60 may be made thinner than the central 
panel 51 for still greater flexability. 
In order to counterbalance the flexibility provided by the thin wall and 
multiple flex points of the panel, it is necessary to stiffen the post 
walls 40 to provide the necessary resistance to vacuum deformation, while 
still providing a squeezable bottle which will not permanently dent when 
squeezed. To increase the post wall stiffness, there are preferably 
provided substantially perpendicular junctions between second step 64 and 
post wall 40, and between second step 64 and first step 63. These 
junctions preferably range from about 80.degree. to about 100.degree., and 
more preferably about 85.degree. to about 95.degree.. Also, in order to 
insure sufficient stiffness in the post wall, the post depth (i.e., 
D.sub.1 -D.sub.2) is preferably about 0.08 inches (2 mm) to about 0.16 
inches (4 mm), which corresponds to the radial depth of the second 
connecting wall. 
FIGS. 8-9 show an alternative embodiment, wherein an additional 
vertically-elongated reinforcing rib 180 is provided to further stiffen 
the post walls. Alternative container 110 is substantially the same as 
previously defined container 10, and similar portions have been given 
similar number designations in the "100" series. Thus, container 110 has 
an upper bumper 120, lower bumper 124, and a panel section 122. 
Surrounding each vacuum panel 150 are post walls 140, including upper post 
wall 141, lower post wall 142, and median post walls 143. Down the center 
of each median post wall 143 is a vertically elongated and radially 
inwardly recessed rib 180. Again, each vacuum panel includes a lowermost 
flex point 153 and stepped connecting walls. 
The present invention has applications beyond the illustrated beverage 
container with nozzle for use by athletes. More generally, the container 
may be used for any cosmetic, food, beverage, etc., product which requires 
a squeezable container with panels. The product may be pressurized, e.g., 
beer, or nonpressurized, e.g., juice. The container may be used with 
cold-fill products, wherein the stepped panel construction provides ready 
squeezability with "bounce back" to resist denting. 
The container may be made in a variety of sizes (volume) and shapes (height 
and diameter). For example, one-gallon hot fill squeezable PET beverage 
container may have a six-inch diameter and an average panel wall thickness 
of about 0.017 inches (44 mm) to about 0.020 inches (51 mm). 
The preferred thermoplastic resins useful for making a hot-fill container 
of this invention include polyester, polypropylene, polycarbonate, 
polyacrylonitrile, polyvinyl chloride and polyethylene napthalene. 
The preferred polyester resins are usually polyesters wherein more than 80 
mol %, and preferably more than 90 mol % of the acid component is 
terephthalic acid and more than 80 mol %, and preferably more than 90 mol 
% of the glycol component is isophthalic acid (IPA), diphenylether 
4,4'-dicarboxylic acid, naphthalene-1,4 or 2,6-dicarboxylic acid, adipic 
acid, sebasic acid, decane 1,10-dicarboxylic acid and 
hexahydroterephthalic acid. Examples of the residual qlycol component are 
propylene glycol, 1,4-butane diol, neopentyl glycol, diethylene glycol, 
cyclohexane dimethanol (CHDM), 2,2-bis(4-hydroxyphenyl)- propane and 
2,2-bis(4hydroxyethoxyphenyl)propane. Also available are polyester resins 
containing p-oxybenzoic acid, etc. as an oxyacid. 
The intrinsic viscosity of these thermoplastic polyester resins is 
approximately 0.55 or more, preferably about 0.65 to about 1.4, and more 
preferably about 0.8 to about 0.9. When the intrinsic viscosity is less 
than 0.55, it is difficult to obtain a preform which is transparent and 
amorphous. In addition, the mechanical strength of the resulting container 
is not sufficient. Intrinsic viscosity measurements are made according to 
the procedure of ASTM D-2857, by employing 0.0050.+-.0.0002 g/ml of the 
polymer in a solvent comprising o-chlorophenol (melting point 0.degree. 
C.), at 30.degree. C. Intrinsic viscosity (I.V.) is given by the formula: 
EQU I.V.=(1n(V.sub.Soln. /V.sub.Sol.))/C 
where: 
V.sub.Soln. is the viscosity of the solution in any units; 
V.sub.Sol. is the viscosity of the solvent in the same units; and 
C is the concentration in grams of polymer per 100 mls of solution. 
PET copolymer resins useful in this invention are commercially available 
and include copolymers having 4-6% by total weight of a comonomer such as 
1,4-cyclohexanedimethanol (CHDM) and/or isophthalic acid (IPA). These 
materials are commercially available from Eastman Chemical Company in 
Kingsport, Tennessee, and Goodyear Tire & Rubber Co. in Akron, Ohio. 
In making the preferred polyester container from an amorphous preform 
according to the reheat stretch blow process, a suitable stretching 
temperature range is about 70.degree.-130.degree. C. It is advisable to 
stretch the preform about 2-4 times in an axial direction and about 3-5 
times in a circumferential direction. A more preferable condition is 6-15 
times in terms of a stretch ratio for area--and more preferably about 7-11 
times in the panel section. 
It may also be useful to provide a multi-layer preform, e.g., with one or 
more barrier layers, for a specific product which is degraded by oxygen, 
moisture, light, etc. 
Although certain preferred embodiments of the invention have been 
specifically illustrated and described herein, it is to be understood that 
variations may be made without departing from the spirit and scope of the 
invention as defined by the appended claims. Thus, all variations are to 
be considered as part of the invention as defined by the following claims.