US20100176081A1

US20100176081A1 - Container having meta-stable panels

Info

Publication number: US20100176081A1
Application number: US12/531,401
Authority: US
Inventors: Satya Kamineni; Timothy J. Boyd; Michael R. Mooney
Original assignee: Constar International LLC
Current assignee: Constar International LLC
Priority date: 2007-03-16
Filing date: 2008-03-14
Publication date: 2010-07-15
Also published as: WO2008115810A1

Abstract

A container has meta-stable panels to compensate for internal vacuum from hot filling. The panels include a groove that yields during deformation such that the stiffness of the panel varies from its pre-yield stage to its post-yield stage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional application No. 60/895,288 filed Mar. 16, 2007, which is incorporated by reference herein in its entirety.

BACKGROUND

The present invention relates to the structure and function of containers, and more particularly to containers capable of receiving hot fluids and having panels capable of inward deflection, and methods relating to same.
Perishable beverage and food products are often placed into containers at elevated temperatures. In a conventional hot-fill process, the liquid or flowable product is charged into a container at elevated temperatures, such as 180 to 190 degrees F., under approximately atmospheric pressure. Because a cap hermetically seals the product within the container while the product is at the hot-filling temperature, hot-fill plastic containers are subject to negative internal pressure (that is, relative to ambient pressure) upon cooling and contraction of the products and any entrapped air in the head-space. The phrase hot filling as used in the description encompasses filling a container with a product at an elevated temperature, capping or sealing the container, and allowing the package to cool.
It has been a goal of conventional hot-fill container design to form bodies that have a desired and predictable shape after hot filling. For example, containers having an approximately cylindrical body or a circular transverse cross section, the goal has been to retain the shape after the hot filling process. To promote this goal, conventional hot-fill containers include designated flexing portions—vacuum panels—that deform when subjected to typical negative internal pressures resulting from the hot filling process. The inward deflection of the vacuum panels tends to equalize the pressure differential between the interior and exterior of the container to enhance the ability of the cylindrical sections to maintain an attractive shape, to enhance the ease of labeling, or provide like benefit.
Some container designs are symmetric about a longitudinal centerline and designed with stiffeners to maintain the intended cylindrical shape while the vacuum panels deflect. For example, U.S. Pat. Nos. 5,178,289; 5,092,475; and 5,054,632 teach stiffening portions or ribs to increase hoop stiffness and eliminate bulges while integral vacuum panels collapse inwardly. U.S. Pat. No. 4,863,046 is designed to provide volumetric shrinkage of less than one percent in hot-fill applications.
Other containers include a pair of vacuum panels, each of which has an indentation or grip portion enabling the container to be gripped between a user's thumb and fingers. For example, U.S. Pat. No. 5,141,120 teaches a bottle having a hinge continuously surrounding a vacuum panel, which includes indentations for gripping. In response to cooling of the container contents, the hinge enables the entire vacuum panel to collapse inwardly.
For most conventional hot fill bottles, a graph of internal pressure vs. volumetric displacement in response to internal vacuum is a straight line. Some references disclose vacuum panels in hot fill containers having portions that invert from an outwardly bulged state to an inwardly bulged state during the deflection process. For example, U.S. Pat. No. 5,141,121 discloses a vacuum panel having an outwardly bulged surface that inverts relative to a vertical plane in response to internal vacuum. U.S. patent application Ser. No. 10/361,356 (Lane) discloses a vacuum panel for a hot fill container having a compound curve and indents. A central portion of the vacuum panel inverts to produce a sharp downward deviation in the graph of internal vacuum versus volume displacement represented in FIG. 7 of the 356 application. Outside of the panel inversions, the graph of FIG. 7 of the 356 application is a series of straight lines that appear to share approximately the same slope.

SUMMARY

As plastic blow-molded bottles are engineered to decrease their weight, new vacuum panel technology is required. Accordingly, a container having at least one metastable volume compensation panel is provided. The metastable panel may have a first stiffness, undergoes a buckling or like phenomenon, and has a second stiffness after buckling. Preferably, the buckling (or the like phenomenon) occurs in a local or small area and enables the change in stiffness.
A plastic bottle suitable for hot-filling comprises an enclosed circular base; an upper portion including an opening; and a body disposed between the base and the upper portion. The body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to negative pressure after hot filling, such that during a pre-yielding stage, the vacuum panel deflects inwardly at a first stiffness and, during a post-yielding stage, the vacuum panel deflects inwardly at a second stiffness. Preferably, a portion of the panel yields during the inward deflection, thereby facilitating a change in stiffness, and the first stiffness does not equal the second stiffness. Preferably, the yielding stage includes buckling.
Each panels may include a groove disposed between a pair of fields. In this configuration, a portion of the groove slowly gives way during said inward deflection, thereby facilitating the stiffness variation, or a portion of the groove buckles during said inward deflection, thereby facilitating the stiffness variation. Each panel may also include a pair of opposing rim walls, a pair of raised fields disposed within said edge, and a groove disposed between the fields. The rim walls is located proximate a corresponding edge of the body sidewall.
The bottom the groove is higher than a bottom of the rim walls, and each one of an uppermost portion of the fields is higher than the bottom of the groove. The grove has a pair of opposing end walls that extend inwardly from the groove bottom to the rim walls, and the groove extends approximately from one of the rim walls approximately to the opposing rim. In some configurations, the end walls buckle in response to the negative pressure. Often, it is the buckling that enables inward movement of the groove.
According to another embodiment, a plastic bottle suitable for hot-filling comprises an enclosed circular base; an upper portion including an opening; and a body located between the base and the upper portion. The body includes a sidewall and at least two volume compensation panels that deflect inwardly after hot-filling. Each one of the panels includes an upper field, a lower field, and a rib that is disposed between the upper and lower fields and that includes an oblique portion that buckles during the volume compensation process. The buckling facilitates inward movement of the upper and lower fields changes the stiffness from a pre-buckling value to a post-buckling value. Preferably, the oblique portion of the rib is located at an end of a bottom of the rib and forms an oblique angle with a bottom of the rib and is not tangential to the body sidewall. Preferably, the rib has sidewalls that extend upwardly from the rib bottom and connect to the fields, which have an approximately flat surface.
According to another aspect of the invention, a method of absorbing negative pressure within a hot-filled plastic bottle comprises the steps of providing a bottle and filling the bottle with a liquid product at an elevated temperature and sealing or capping the opening. The bottle has an enclosed circular base; an upper portion including an opening; and a body located between the base and the upper portion. The body includes a sidewall and at least two volume compensation panels, as generally described above. The method also includes that at least a portion of the panels deflect inwardly after the filling and sealing step in response to negative pressure within the bottle. The inward deflection includes a first main stage wherein the volume compensation panels exhibit a first stiffness and a second main stage wherein the volume compensation panels exhibit a second stiffness.
According to another embodiment, a plastic bottle suitable for a hot-filling process in which internal vacuum is created comprises an enclosed circular base, an upper portion including an opening; and a body located between the base and the upper portion. The body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to vacuum after hot filling. The panel has an upper field, a lower field, and a hinge located between the upper and lower fields, such that deformation of the panel in response to vacuum occurs in a first stage, a transition stage after the first stage, and a second stage after the transition stage; such that: (i) in the first stage the upper field and lower field are gradually drawn inwardly in response to vacuum; (ii) the transition stage is unstable such that at least a portion of the panel jumps from the first yielding stage to the second yielding stage; and (iii) in the second yielding stage the upper field and lower field are gradually drawn inwardly in response to vacuum.
For this embodiment, preferably, each of the upper field and the lower field have an inner end located proximate the hinge and an outer end located distal from the hinge, and the inward deformation of each field inner end is greater than the deformation of the each field outer end. Also preferably, the inward deformation of each field inner end is greater than the deformation of the each field at its longitudinal center. And wherein, in longitudinal cross section, a line between the upper field outer end and the upper field inner end forms an internal angle with a line between the lower filed outer end and the upper field inner end, and the angle is less than 180 degrees. This angle may go to approximately 180 degrees or more after vacuum deformation is complete.
Preferably, the inner end of the upper field is located at the lowermost end of the upper field, and the inner end of lower field is located at the uppermost end of the lower field, and the hinge is formed by an approximately horizontal groove.
A plastic bottle suitable for a hot-filling process in which internal vacuum is created comprising an enclosed circular base; an upper portion including an opening; and a body located between the base and the upper portion. The body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to vacuum after hot filling. The panel has an upper field, a lower field, and an interruption separating the upper field from the lower field. Each one of the upper field and the lower field forms a peak before the bottle is deformed by the vacuum, the lower field peak is located opposite the upper field peak relative to the interruption. The deformation of the panel in response to vacuum occurs in a first stage, a transition stage after the first stage, and a second stage after the transition stage; such that: (i) in the first stage the upper field and lower field are gradually drawn inwardly in response to vacuum; (ii) the transition stage in which at least a portion of the panel jumps from the first yielding stage to the second yielding stage; and (iii) in the second yielding stage the upper field and lower field are gradually drawn inwardly in response to vacuum, and wherein radial height, relative to other portions of the fields, of each of the peaks is reduced upon vacuum deformation.
According to another embodiment, a plastic bottle suitable for a hot-filling process in which internal vacuum is created comprises an enclosed circular base; an upper portion including an opening; and a body located between the base and the upper portion. The body includes a sidewall and at least one volume compensation panel including: an upper field that, in longitudinal cross section, has a radial peak; a lower field that, in longitudinal cross section, has a radial peak; an approximately horizontal groove, located between the upper field and the lower field, that separates the upper field peak from the lower field peak; wherein radial height, relative to other portions of the fields, of each of the peaks is reduced upon vacuum deformation. A groove may extend around the panel and merge with the sidewall. Preferably, the peaks are distal to the upper and lower edges of the panel and each one of the fields has a width proximate its peak that is smaller than a width proximate the upper and lower edges of the field, whereby the panels and groove form an hourglass shape.
The upper field preferably has a width that gradually narrows from its upper edge to its peak and the lower field has a width gradually narrows from its lower edge to its peak. A pair of opposing inclined walls may extend from the groove along side edges of the panel generally radially outwardly to side edges of the fields and to the groove.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a first container illustrating a first embodiment of the vacuum absorption panel before filling;

FIG. 2 is a first side elevational view of the container shown in FIG. 1;

FIG. 3 is a second side elevational view of the container shown in FIG. 2;

FIG. 4A is an enlarged longitudinal cross sectional view taken through lines IV-IV in FIG. 2 showing the container in its as-molded state;

FIG. 4B is the longitudinal cross-sectional view shown in FIG. 4A showing the container in its as-molded state in dashed lines and in its filled & cooled or deformed state in solid lines;

FIG. 5A is a transverse cross-sectional view taken through lines V-V in FIG. 2 showing the container in its as-molded state in dashed lines and in a partially deformed state in solid lines;

FIG. 5B is a transverse cross-sectional view taken through lines V-V in FIG. 2 showing the container in its as-molded state in dashed lines and in its filled & cooled or deformed state in solid lines;

FIG. 6A is a side elevational view of a second container having a second embodiment of the vacuum absorption panel;

FIG. 6B is a side elevational view of a variation of or modification to second embodiment container;

FIG. 7A is a side elevational view of the second embodiment container taken perpendicular to the view of FIG. 6A;

FIG. 7B is a side elevational view of the second embodiment container taken perpendicular to the view of FIG. 6B;

FIG. 8A is a transverse cross-sectional view of the second container taken through lines VIII-VIII in FIG. 7B;

FIG. 8B is a transverse cross-sectional view of the second container taken through lines VIII-VIII in FIG. 7B and showing the container in its as-molded and fully deformed states;

FIG. 9A is a longitudinal cross-sectional view of the second container taken through line IX-IX in FIG. 6A;

FIG. 9B is a longitudinal cross-sectional view of the second container taken through line IX-IX in FIG. 6A and showing the container in its as-molded state and deformed state;

FIG. 10 is a gray-scale solid model perspective image of a third embodiment container; FIG. 10′ is a color solid model perspective image of the third embodiment container;

FIG. 11 is a side elevational view of the container of FIG. 10;

FIG. 12 is a side elevational view of the container of FIG. 10 taken perpendicular to the view of FIG. 11;

FIG. 13 is a longitudinal cross-sectional view taken through line XIII-XIII in FIG. 11 and showing the container its as-molded state and deformed state;

FIG. 14 is a transverse cross-sectional view taken through line XIV-XIV in FIG. 11 and showing the container its as-molded state and deformed state;

FIG. 15 is a gray-scale solid model perspective images of a fourth embodiment container; FIG. 15′ is a color solid model perspective image of the fourth embodiment container;

FIG. 16 is an ideal graph of vacuum pressure versus deflection at the center of the volume compensation panel of the first embodiment container shown in FIG. 1;

FIG. 17 is a calculated plot of vacuum pressure versus deflection at the center of a volume compensation panel of the first embodiment container shown in FIG. 1;

FIG. 18A is a plot of vacuum pressure versus deflection at the center node of the panel of the second embodiment container shown in FIG. 6A upon hot filling;

FIG. 18B is a plot of vacuum pressure versus container volume upon hot filling of the second embodiment container shown in FIG. 6A;

FIG. 19A is a plot of vacuum pressure versus deflection at the center node of the panel of third embodiment container shown in FIG. 10 upon hot filling;

FIG. 19B is a plot of vacuum pressure versus container volume upon hot filling of the third embodiment container shown in FIG. 10;

FIG. 20 is a plot of vacuum pressure versus container volume upon hot filling of the fourth embodiment container shown in FIG. 15;

FIG. 21A is a three dimensional plot of deformation under hot fill conditions of first embodiment container shown in FIG. 15;

FIG. 21B is a three dimensional plot of stress under hot fill conditions of first embodiment container shown in FIG. 15;

FIG. 22A is a three dimensional plot of radial deformation under hot fill conditions of the third embodiment container shown in FIG. 10;

FIG. 22B is a three dimensional plot of overall deformation under hot fill conditions of the third embodiment container shown in FIG. 10;

FIG. 22C is a three dimensional plot of stress under hot fill conditions of the third embodiment container shown in FIG. 10;

FIG. 23A is a three dimensional plot of radial deformation under hot fill conditions of the fourth embodiment container shown in FIG. 15;

FIG. 23B is a three dimensional plot of overall deformation under hot fill conditions of the fourth embodiment container shown in FIG. 15; and

FIG. 23C is a three dimensional plot of stress under hot fill conditions of the fourth embodiment container shown in FIG. 15.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This description includes four embodiments reflecting aspects of the present invention. The embodiments are illustrated by respective reference numerals 10, 110, 210, and 310. As illustrated in FIG. 1 through FIG. 3, container 10 according to the first embodiment includes a base 12, a body 14, an upper portion such as dome 16, and a finish 20.
Base 12 encompasses any type, and preferably includes a heel 24, a standing ring 26, and a reentrant portion 28. Preferably, an upper and lower shoulder 19 a and 19 b define a label panel. Container embodiment 10 does not have a continuous waist, as it includes spaced-apart ribs 18 a and 18 b in the upper and lower portions of the body 14. Body 14 may be considered to be the portion between upper and lower waists or ribs 18 a and 18 b.
Dome 16 extends upwardly from body 14 or upper shoulder 19 a. Dome 16 preferably narrows to finish 20, which has threads for engaging threads on a closure 22 that covers a pour opening 21. A closure 22 for engagement with finish 18 is illustrated diagrammatically in FIG. 2. Each of the container embodiments is suitable for use with a closure.
Body 14 includes at least one volume absorption panel 30 located in bottle sidewall 32. As shown in the embodiment of FIG. 1, body 14 may have a pair of opposing panels 30 that are spaced 180 degrees apart.
Panel 30 includes upper and lower fields 36 a and 36 b, and a rib or groove 38. Groove 38 functions as a hinge or trigger such that upon sufficient activation energy or upon critical portions of groove 38 reaching their yield points, it yields to enable panel 30 to flex, as described more fully herein. Each opposing side of panel 30 includes a rim 34 that merges into container sidewall 32. Each rim 34 preferably is substantially straight and vertical, even though the present invention encompasses panels of any overall shape.
Each field 36 a and 36 b includes a field surface 46 (designated 46 a and 46 b to indicate the corresponding upper and lower field surfaces) and opposing transition sidewalls 48 that extend between field surfaces 46 a and 46 b to container rims 34. Each field surface 46 a and 146 b preferably is nearly flat (in transverse cross section), formed by a single large radius, or other shape described more fully below. The bottommost surface (in transverse cross section) of the intersection of sidewalls 48 and rims 34 is indicated by reference numeral 44 on FIGS. 5A and 5B.
Upper field 36 a has an upper wall 50 a and lower field 36 b has a lower wall 50 b that merge respectively into upper and lower ribs, as best shown in FIGS. 4A and 4B. Upper wall 50 a and lower wall 50 b are referred to together as outboard walls 50. The lower part of upper field 36 a and the upper part of lower field 36 b merge into groove 38. Each field surface 46 a and 46 b preferably has a relatively large surface area (compared, for example, to the surfaces of groove 38 or transition walls 48).
Each field surface 46 a and 46 b is wider near its outboard end (that is, near the uppermost and lower most ends of panel 30) than near its inboard end (that is, near the center of the panel 30) such that each upper and lower field surface 46 a and 46 b forms an approximate lobe-shape and together approximately form an hourglass shape that is interrupted by groove 38. As opposing rims 34 are parallel in the embodiment of FIG. 1, each transition sidewall 48 forms an approximately triangular shape or D-shape, although the present invention encompasses other shapes.
Groove 38 preferably is at the center of panel 30 and horizontal. Groove 38 includes generally opposing groove walls 58 that are preferably straight and that terminate at a groove bottom 60, as best shown in FIGS. 4A and 4B. Groove walls preferably form an internal angle of 120 degrees, as illustrated in FIG. 4A, and preferably smoothly merges into transition sidewalls 48 at points designated by reference numeral 64 in FIGS. 5A and 5B.
Preferably, a radial position or height (that is, the radial dimension in transverse cross section) of each field surface 46 a and 46 b is greater than the height of the groove bottom 60, and groove bottom 60 has a radial position or height greater than rim bottom surface 44. Preferably, panel 30 is meta-stable, as described below in the discussion of the function of panel 30.
For the particular 20 ounce container configuration shown in FIG. 1, field heights D1 and D2, which represent the heights of the (longitudinally) innermost and uppermost portions of the field surfaces 46 a and 46 b, are 0.138 inches and 0.044 inches, respectively, as measured from a straight line between the upper and lower grooves 18 a and 18 b, as shown in FIG. 4A. The depth D3 of groove 38 (relative to sidewall 32) is approximately 0.100. The depth D4 (relative to sidewall 32) of grooves 18 a and 18 b is 0.190 inches. These dimensions are not intended to limit the scope of the invention, but rather provide specific examples of structure that the inventors believe will function as described herein.
As best shown in FIG. 3, FIG. 4A, and FIG. 4B, panel 30 preferably bulges slightly outwardly in its as-molded state when viewed in longitudinal cross section. Preferably, panel 30 in its fully deformed state is generally longitudinal such that field surfaces 46 are approximately parallel. FIG. 5A shows container 10 in its as-molded state in dashed lines and in an intermediate state (that is, partly deformed) under vacuum conditions and near its point of instability, as explained more fully below, in solid lines. End points of groove 38 are indicated by reference numeral 64 in the as-molded state and by reference numeral 64′ in its intermediate or partly deformed state. FIG. 5B shows container 10 in its fully deformed state in which groove ends, designated by reference numeral 64″, have yielded or buckled, also referred to as jumped, such that is has reached a second point, after which deformation is not non-linear. Preferably, groove bottom 60 is approximately inline with end sidewalls 48 in the fully deformed state, as illustrated in FIG. 5B.
A container second embodiment 110 is illustrated in FIGS. 6A, 6B, 7A, 7B, 8A, 8B, 9A, and 9B. The embodiment shown in FIGS. 6A and 7A is identical to the embodiment shown in FIGS. 6B, 7B, and 8 except a center rib is omitted from the sidewall of the latter, which is designated by reference numeral 110′, for help in illustrating the transverse cross section. Accordingly, the description of container 110 also applies to container 110′.
Container 110 includes a base 112, a body 114, an upper portion such as dome 116, a waist 118, and a finish 120. Base 112 encompasses any type, and preferably includes a heel 124, a standing ring 126, and a reentrant portion 128. Preferably, upper and lower shoulders 119 a and 119 b define a label panel. Dome 116 extends upwardly from body 114 or upper shoulder 119 a. Dome 116 preferably narrows to finish 120 that has threads for engaging threads on a closure, which is omitted from the figures showing the second embodiment 110 for clarity.
Body 114 includes at least one volume absorption panel 130 located in bottle sidewall 132. Body 114 may have a pair of opposing panels 130 that are spaced 180 degrees apart.
Panel 130 includes upper and lower fields 136 a and 136 b, and a rib or groove 138. Groove 138 functions as a hinge or trigger such that upon sufficient activation energy or upon critical portions of groove 38 reaching their yield points, it yields to enable panel 30 to flex, as described more fully herein Each opposing side of panel 130 includes a rim 134 that merges into container sidewall 132. Each rim 134 preferably is substantially straight and vertical, even though the present invention encompasses panels of any overall shape.
Each field 136 a and 136 b includes a field surface 146 (designated 146 a and 146 b to indicate the corresponding upper and lower field surfaces) and opposing transition sidewalls 148 that extend between field surfaces 146 a and 146 b to container rims 134. The bottommost surface (in transverse cross section) of the intersection of sidewalls 148 and rims 134 is indicated by reference numeral 144 on FIG. 8.
Upper field 136 a has an upper wall 150 a and lower field 136 b has a lower wall 150 b that merge respectively into upper and portions of rim 134. Upper wall 150 a and lower wall 150 b are referred to together as outboard walls 150. The lower part of upper field 136 a and the upper part of lower field 136 b merge into groove 138. Each field surface 146 a and 146 b preferably has relatively large surface area (compared, for example to the surfaces of groove 138 or transition walls 148).
Each field surface 146 a and 146 b is wider near its outboard end (that is, near the uppermost and lower most ends of panel 130) than near its inboard end (that is, near the center of the panel 130) such that each upper and lower field surface 146 a and 146 b forms an approximate lobe-shape and together approximately form an hourglass shape that is interrupted by groove 138. As opposing rims 134 are parallel in the embodiment of FIG. 1, each transition sidewall 148 forms an approximately triangular shape or D-shape, although the present invention encompasses other shapes.
Groove 138 preferably is at the center of panel 30 and horizontal. Groove 138 includes generally opposing groove walls 158 that are preferably straight and that terminate at a groove bottom 160, as best shown in FIG. 8. Groove walls preferably form an internal angle of 120 degrees in transverse cross section, but the present invention encompasses any configuration. Groove 138 preferably smoothly merges into transition sidewalls 148 at points designated by reference numeral 164.
Container 110 has a volumetric capacity of 20 ounces; the heights and depths of panel 130 are approximately those provided for first embodiment container 10. Referring to FIGS. 8A, 8B, 9A, and 9B to illustrate additional dimensions and relationships, dimension D5 between surface 144 and groove bottom 160 is 0.090 inches. The vertical portions of transition wall 148 form an angle A2 of 35 degrees from a reference line equidistant between opposing panels 130 or parallel to groove 138. Transition wall 148 and vertical rim 134 form an internal angle A3 of 85 degrees. The upper and lower portions of rim 134 approximately form an angle A4 of 60 degrees relative to a vertical reference line.
As best shown in FIG. 9A, groove walls 158 form an internal angle A5 of 120 degrees. Groove 138 preferably has a radius R1 of 0.20 inches at its bottom 160 and a radius R2 of 0.50 inches between groove walls 158 and field surfaces 146 a and 146 b. Each field surface 146 a and 146 b is formed by a single radius R3 of approximately 9.4 inches. The present invention encompasses field surfaces 146 a and 146 b (and of the other embodiments described herein) having shapes, in transverse cross section, other than a single radius, including being flat or approximately flat, having a radius that changes gradually or at a constant rate, or several radiuses that merge.
FIG. 8 b and FIG. 9B illustrate container 110 in its as-mold state in solid lines and in its deformed state under normal vacuum conditions associated with hot filling in dashed lines. Panel 130 preferably bulges slightly outwardly in its as-molded state when viewed in longitudinal cross section. Preferably, panel 130 in its fully deformed state is generally longitudinal such that field surfaces 146 a and 146 b are approximately parallel. In its deformed state, groove ends 64″ preferably are line with groove bottom 60.
A container third embodiment 210 is illustrated in FIGS. 10, 11, 12, 13 and 14. Container 210 includes a base 212 a body 214, an upper portion such as dome 216, a waist 218, and a finish 220 (not shown in figures for third embodiment container 210).
Base 212 encompasses any type, and preferably includes a heel 224, a standing ring 226, and a reentrant portion 228. An upper and lower shoulder 219 a and 219 b define a label panel. Dome 216 extends upwardly from body 214 or upper shoulder 219 a. Dome 216 preferably narrows to finish 220 that has threads for engaging threads on a closure 222.
Body 214 includes at least one volume absorption panel 230 located in bottle sidewall 232. Body 214 may have a pair of opposing panels 230 that are spaced 180 degrees apart.
Panel 230 includes upper and lower fields 236 a and 236 b, a horizontal rib or groove 238 separating the fields, and a vertical groove 239. Each opposing side of panel 230 includes a rim 234 that merges into container sidewall 232. Each rim 234 preferably is substantially straight and vertical, even though the present invention encompasses panels of any overall shape.
Each field 236 a and 236 b includes a field surface 246 (designated 246 a and 246 b to indicate the corresponding upper and lower field surfaces) and opposing transition sidewalls 248 that extend between field surfaces 246 a and 246 b to container rims 234. The bottommost surface of the intersection of sidewalls 248 and rims 234 is indicated by reference numeral 244 on FIG. 14.
Upper field 236 a has an upper wall 250 a and lower field 236 b has a lower wall 250 b that merge respectively into upper and portions of rim 234. Upper wall 250 a and lower wall 250 b are referred to together as outboard walls 250. The lower part of upper field 236 a and the upper part of lower field 236 b merge into groove 238. Each field surface 246 a and 246 b preferably has relatively large surface area (compared, for example to the surfaces of groove 238 or transition walls 234).
Each field surface 246 a and 246 b is wider near its outboard end (that is, near the uppermost and lower most ends of panel 230) than near its inboard end (that is, near the center of the panel 230) such that each upper and lower field surface 246 a and 246 b forms an approximate lobe-shape and together approximately form an hourglass shape that is interrupted by groove 238. As opposing rims 234 are parallel, each transition sidewall 248 forms an approximately triangular shape or D-shape, although the present invention encompasses other shapes.
Groove 238 preferably is at the center of panel and horizontal. Groove 238 includes generally opposing groove walls 258 that are preferably straight and that terminate at a groove bottom 260. Groove walls preferably form an internal angle of 120 degrees in transverse cross section, but the present invention encompasses any configuration. Groove 238 preferably smoothly merges into transition sidewalls 248 at points designated by reference numeral 264.
Container 210 has a volumetric capacity of 20 ounces and the panel 230 dimensions may be approximately the same as those of second embodiment container 110. FIG. 13 and FIG. 14 illustrate container 210 in its as-mold state in solid lines and in its deformed state under normal vacuum conditions associated with hot filling in dashed lines. Panel 230 preferably bulges slightly outwardly in its as-molded state and is concave in its fully deformed state when viewed in when viewed in longitudinal cross section. Panel 230 in its fully deformed state is concave when viewed in transverse cross section.
Groove 38 functions as a hinge or trigger such that, upon sufficient activation energy or upon critical portions of groove 38 reaching their yield points, it yields to enable panel 30 to flex, as described more fully herein. Vertical groove 239 preferably is equidistant from groove ends 264 and perpendicular to the longitudinal axis of groove 238. Groove 239 extends into fields 246 a and 246 b and, preferably, does not extend fully to the upper and lower portions of rim 234.
To achieve the concave shape, vertical groove 239 may act as a hinge or lower the activation energy required for panel 230 to reach the yielding or buckling stage. In some embodiments, small regions of panel 230 near groove ends 264 are high stress regions that reach their yield points and buckle to enable the overall panel perform as described herein.
A container fourth embodiment 310, illustrated in FIG. 15, has the same structure as third embodiment container 210 in its base 312, dome 316, waist 318, finish 320, and sidewall 32. Its panels 330 have the same rim 334 and transition sidewalls 348 as third embodiment container 210 such that fields 346 a and 346 b have the same outline shape as that of third embodiment panels 230.
Each panel 330 includes a pair of groove segments 328 a and 328 b. Outboard ends 364 of groove segments 238 a and 238 b merge smoothly into transition sidewalls 348. Segments 328 a is spaced apart from segment 328 b by an intermediate space 329 that merges smoothly into fields 349 a and 349 b.
Preferably the bottle sidewall for each embodiment (that is, sidewalls 32, 132, 232, and 232) is generally cylindrical with horizontal ribs; the invention encompasses sidewalls of any shape. The present invention is not limited to a particular number of panels, nor to their size, overall shape, or relative spacing about the container's circumference. The number of panels may be chosen according to well-known parameters that will be understood by persons familiar with hot-fill bottle technology upon reading the present disclosure. Also, the bodies of each embodiment may include additional structure, including but not limited to conventional or other panels not covered by the present invention.
The disclosed dimensions and angles are not intended to limit the scope of the invention, but rather provide specific examples of structure. The present invention is not limited to a particular configuration or geometries, but rather the scope is controlled by the language of the claims Variations in the components are encompassed by the present invention, as will be understood by persons familiar with bottle engineering and manufacturing upon considering this disclosure.
Preferably, containers 10, 110, 210, and 310 are formed of a conventional PET, and any other suitable material is contemplated. The container embodiments having the features described herein may be formed of a relatively thinner sidewall. The thin sidewalls, in some circumstances, may aid in the yielding (including reaching the elastic limit of the material or other modes of giving way) of portions of the containers (such as at intersections 64, 164, 264, and 364). Accordingly, the present panels are suitable for lightweight containers.
The following description of the operation refers to components of first embodiment container 10 for convenience, but is equally applicable to the function of containers 110, 210, and 310 unless stated otherwise. After container 10 is fill with a liquid product at an elevated temperature, such as 185° F., it is sealed and capped by closure 22. During subsequent cooling, the liquid product and any air in the headspace between the liquid and the seal cools and contracts. The plastic material of container 10 may also undergo shrinkage that reduces its volume, but the container shrinkage is typically small compared to the product and headspace gas shrinkage. Accordingly, an internal negative pressure acts on container 10.
FIG. 16 is an ideal graph of internal container pressure versus the magnitude of inward deflection of the center node (such as in the geometric center of groove 38) of a panel, such as panel 30, to illustrate the function of the panels disclosed herein. As used herein, “stiffness” generally refers to mechanical stiffness, and more particularly is defined as the local slope of the pressure versus deflection curve, such as the ideal curve shown in FIG. 16.
The panel undergoes at least three distinct stages of deformation: a pre-yield stage, a yielding stage, and a post-yield stage. The term yield, as used herein, encompasses buckling—that is, relatively sudden movement from one state or position to another state or position—and a slow progression from one state or position to another state or position. The containers described herein may function as described herein, it is surmised, because a portion of the panel material (such as near groove end 64, 164, 264, and 364) reaches a yield point on the stress-strain curve such that the portion reaches its elastic limit; the present invention is not limited to structure that functions according to this principle, but also encompasses the other means for enabling the panel to give way in a manner in which no portion of the structure reaches its yield point. Further, the present invention encompasses the structure defined in the claims, regardless of its function.
During the pre-yield stage or pre-buckling stage, which is identified by reference letter A in the idealized chart in FIG. 16, a portion of the panel builds up activation energy in preparation of yielding. During the pre-yielding stage, the panel exhibits a constant stiffness modulus M_Aor a stiffness that only changes slightly. When used to refer to stiffness, the term “constant” encompasses some variation is the linearity of a plot as long as it is reflected by a smooth and gentle curve.
During the yielding stage, which is indicated by region B in FIG. 16, a portion of the panel buckles or in some other way yields, and the panel exhibits a constant stiffness modulus M_Bor a stiffness that only changes slightly. During the post-yield stage, which is identified by reference letter C in FIG. 16, the yielding portion has released its activation energy, and the panel exhibits a constant stiffness modulus M_Cor a stiffness that only changes slightly.
FIG. 17 is a calculated plot of internal bottle pressure versus magnitude of inward deflection of a center node—that is, a geometric center of groove 38—of container 10 having panels 30 as described above upon hot filling and subsequent cooling. The calculations were performed using finite element analysis. The center node was chosen to isolate the function of panel 30 while the entire container undergoes vacuum absorption. In an initial stage, which is designated by reference letter I₁, the inventors theorize that various portions of the container, such as (possibly) portions of the dome 16, sidewalls 32, bottom 214, and fields 46 a and 46 b, deform with little inward deformation of the center node. Alternatively, panel 30 may function as a conventional panel during this initial stage.
At point p₁, the pre-yield stage B₁begins, in which the predominant vacuum absorption mechanism is inward deflection of panel 30, which is evident by the lower slope manifested in stiffness modulus M_B1. Even though it is likely or possible that the mechanisms of initial deflection stage I₁are at least somewhat still present in pre-yield stage B₁, modulus M_B1is approximately constant.
The inventors theorize that during pre-yield stage B₁, groove end walls 64 deflect as shown in FIG. 5A. Calculated stress is high near the intersection of groove 38 and transition sidewalls 34, as illustrated in the three dimensional plot of stress in FIG. 21B. The intersection is designated by reference numeral 64 in the as-molded, undeformed bottle.
FIG. 5A, which shows groove 38 during pre-yield stage B₁, shows the calculated deformation of groove 38 and the movement of groove end walls 62 relative to groove bottom 60. In general, the extent of yielding or buckling can control the magnitude of volume compensation, as the localized zone of deformation enables larger deformation of the panel. The inventors theorize that local stress at intersections 64 continues to rise (which is also generally referred to as rising activation energy) until reaching the yield stress of the material, at which point q₁the yielding stage C₁begins.
During yielding stage C₁, FIG. 17 illustrates that a large amount of center node deflection occurs relative to vacuum absorption. The inventors theorize that the portions of container 10 proximate intersections 64, upon reaching the elastic limit of its material, yield. The yielding may be sudden, generally referred to herein as buckling, or a slow giving way.
FIG. 5B illustrates groove 38 after yielding has occurred, such as at point r₁in FIG. 17. The solid line illustrating groove 38 shows portion 64″ as a substantially straight portion between transition wall 34 and groove bottom 60, reflecting not only the inward movement of groove bottom 60, but also the overall change in shape of groove 38 and transition wall 34.
FIGS. 18A and 18B provide plots of vacuum pressure versus magnitude of center node deflection and vacuum pressure versus container volume change for second embodiment container 110 upon hot filling and subsequent cooling. FIGS. 19A and 19B provide vacuum pressure versus magnitude of center node deflection and vacuum pressure versus container volume change for third embodiment container 210 upon hot filling and subsequent cooling. FIG. 20 provides vacuum pressure versus container volume change for fourth embodiment container 310 upon hot filling and subsequent cooling.
FIG. 21A and FIG. 21B provide a three dimensional deformation plot and stress plot, respectively, of first embodiment container 10 upon hot filling. FIGS. 22A and 22B provide, for third embodiment container 210, three dimensional plots of radial displacement and displacement, and FIG. 22C provides a three dimensional plot of stress upon hot filling. FIGS. 23A and 23B provide, for fourth embodiment container 310, three dimensional plots of radial displacement and displacement, and FIG. 23C provides a three dimensional plot of stress for hot filling
The description of the function of the container embodiments is directed to preferred embodiments of the structure and function of the present invention, but as is clear from the above description, the invention is not limited to the particular disclosed structure and function. Rather, the scope of the invention should be defined by the language of allowable claims.

Claims

1. A plastic bottle suitable for hot-filling, said bottle comprising:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to negative pressure after hot filling, wherein during a pre-yielding stage, the vacuum panel deflects inwardly at a first stiffness and, during a post-yielding stage, the vacuum panel deflects inwardly at a second stiffness

2. The bottle of claim 1 wherein a portion of the panel yields during the inward deflection, thereby facilitating a change in stiffness.

3. The bottle of claim 2 wherein the first stiffness does not equal the second stiffness.

4. The bottle of claim 1 wherein the yielding stage includes buckling.

5. The bottle of claim 1 wherein each one of the vacuum panels includes a groove disposed between a pair of fields.

6. The bottle of claim 5 wherein a portion of the groove slowly gives way during said inward deflection, thereby facilitating the stiffness variation.

7. The bottle of claim 5 wherein a portion of the groove buckles during said inward deflection, thereby facilitating the stiffness variation.

8. The bottle of claim 7 wherein each one of the vacuum panels further includes:

a pair of opposing rim walls, each one of the rim walls is disposed proximate a corresponding edge of the body sidewall,

a pair of raised fields disposed within said edge, and

a groove disposed between the fields.

9. The bottle of claim 8 wherein a bottom of the groove is higher than a bottom of the rim walls, and each one of an uppermost portion of the fields is higher than the bottom of the groove.

10. The bottle of claim 9 wherein the grove has a pair of opposing end walls that extend inwardly from the groove bottom to the rim walls.

11. The bottle of claim 9 wherein the end walls buckle in response to the negative pressure.

12. The bottle of claim 11 wherein said buckling enables inward movement of the groove.

13. The bottle of claim 1 wherein the groove extends approximately from one of the rim walls approximately to the opposing rim.

14. The bottle of claim 1 wherein the body further includes one or more vacuum panels.

15. A plastic bottle suitable for hot-filling, said bottle comprising:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least two volume compensation panels that deflect inwardly after hot-filling, each one of the panels including an upper field, a lower field, and a rib that is disposed between the upper and lower fields and that includes an oblique portion that buckles during the volume compensation process, said buckling facilitating inward movement of the upper and lower fields changes the stiffness from a pre-buckling value to a post-buckling value.

16. The bottle of claim 15 wherein the oblique portion of the rib is located at an end of a bottom of the rib.

17. The bottle of claim 16 wherein the oblique portion forms an oblique angle with a bottom of the rib and is not tangential to the body sidewall.

18. The bottle of claim 16 wherein the rib has sidewalls that extend upwardly from the rib bottom and connect to the fields.

19. The bottle of claim 18 wherein the fields have an approximately flat surface.

20. A method of absorbing negative pressure within a hot-filled plastic bottle, the method comprising the steps of:

(a) providing a bottle having:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least two volume compensation panels,

(b) filling the bottle with a (liquid) product at an elevated temperature and sealing (capping) the opening; and

(c) at least a portion of the panels deflecting inwardly after the filling and sealing step (b) in response to negative pressure within the bottle, said inward deflection includes a first main stage wherein the volume compensation panels exhibit a first stiffness and a second main stage wherein the volume compensation panels exhibit a second stiffness.

21. The method of claim 20 wherein providing step (a) includes providing a bottle in which each of the vacuum panels includes a rib disposed between opposing fields.

22. The method of claim 21 wherein the rib undergoes a change in shape between the first and second main stages of the deflecting step (c).

23. The method of claim 21 wherein the rib undergoes buckles between the first and second main stages of the deflecting step.

24. The method of claim 19 wherein each one of the vacuum panels includes a groove disposed between a pair of fields.

25. The method of claim 24 wherein a portion of the groove buckles during said inward deflection, thereby facilitating the transition form the first stiffness to the second stiffness.

26. The method of claim 25 wherein each one of the vacuum panels further includes:

a pair of raised fields disposed within said edge, and

a groove disposed between the fields.

27. The method of claim 26 wherein a bottom of the groove is higher than a bottom of the rim walls, and each one of an uppermost portion of the fields is higher than the bottom of the groove.

28. The method of claim 27 wherein the grove has a pair of opposing end walls that extend inwardly from the groove bottom to the rim walls.

29. The method of claim 27 wherein the end walls buckle in response to the negative pressure.

30. The method of claim 29 wherein said buckling enables inward movement of the groove.

31. A plastic bottle suitable for a hot-filling process in which internal vacuum is created, said bottle comprising:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to vacuum after hot filling, the panel having an upper field, a lower field, and a hinge located between the upper and lower fields,

wherein deformation of the panel in response to vacuum occurs in a first stage, a transition stage after the first stage, and a second stage after the transition stage; such that:

(i) in the first stage the upper field and lower field are gradually drawn inwardly in response to vacuum;

(ii) the transition stage is unstable such that at least a portion of the panel jumps from the first yielding stage to the second yielding stage; and

(iii) in the second yielding stage the upper field and lower field are gradually drawn inwardly in response to vacuum.

32. The bottle of claim 1 wherein each of the upper field and the lower field have an inner end located proximate the hinge and an outer end located distal from the hinge, and the inward deformation of each field inner end is greater than the deformation of the each field outer end.

33. The bottle of claim 32 wherein the inward deformation of each field inner end is greater than the deformation of the each field at its longitudinal center.

34. The bottle of claim 32 wherein, in longitudinal cross section, a line between the upper field outer end and the upper field inner end forms an internal angle with a line between the lower filed outer end and the upper field inner end, and the angle is less than 180 degrees.

35. The bottle of claim 34 wherein the angle goes to approximately 180 degrees after vacuum deformation is complete.

36. The bottle of claim 34 wherein the angle goes to greater than 180 degrees after vacuum deformation is complete.

37. The bottle of claim 32 wherein the inner end of the upper field is located at the lowermost end of the upper field, and the inner end of lower field is located at the uppermost end of the lower field.

38. The bottle of claim 32 wherein the hinge is formed by an approximately horizontal groove.

39. The bottle of claim 32 wherein each one of the upper field and the lower field forms an approximately straight line in longitudinal cross section through the center of the panel.

40. The bottle of claim 32 wherein each field has a lobe-like shape.

41. A plastic bottle suitable for a hot-filling process in which internal vacuum is created, said bottle comprising:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to vacuum after hot filling, the panel having an upper field, a lower field, and an approximately horizontal groove between the upper field and lower field,

(ii) the transition stage in which at least a portion of the panel jumps from the first yielding stage to the second yielding stage; and

42. The bottle of claim 41 wherein each one of the upper field and the lower field merge into the groove.

43. The bottle of claim 41 wherein, in longitudinal cross section, the groove has a curved lower wall and a pair of opposing walls.

44. A plastic bottle suitable for a hot-filling process in which internal vacuum is created, said bottle comprising:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least one volume compensation panel that generally deflects inwardly in response to vacuum after hot filling, the panel having an upper field, a lower field, and an interruption separating the upper field from the lower field; each one of the upper field and the lower field forming a peak before the bottle is deformed by the vacuum, the lower field peak is located opposite the upper field peak relative to the interruption;

(iii) in the second yielding stage the upper field and lower field are gradually drawn inwardly in response to vacuum, and

wherein radial height, relative to other portions of the fields, of each of the peaks is reduced upon vacuum deformation.

45. A plastic bottle suitable for a hot-filling process in which internal vacuum is created, said bottle comprising:

an enclosed circular base;

an upper portion including an opening; and

a body disposed between the base and the upper portion, the body includes a sidewall and at least one volume compensation panel including:

an upper field that, in longitudinal cross section, has a radial peak;

a lower field that, in longitudinal cross section, has a radial peak;

an approximately horizontal groove, located between the upper field and the lower field, that separates the upper field peak from the lower field peak;

46. The bottle of claim 45 wherein includes a groove extending around the panel and merging with the sidewall.

47. The bottle of claim 46 wherein the peaks are distal to the upper and lower edges of the panel.

48. The bottle of claim 47 wherein each one of the fields has a width proximate its peak that is smaller than a width proximate the upper and lower edges of the field, whereby the panels and groove form an hourglass shape.

49. The bottle of claim 48 wherein the upper field has a width that gradually narrows from its upper edge to its peak and the lower field has a width gradually narrows from its lower edge to its peak

50. The bottle of claim 49 wherein includes a groove extending around the panel and merging with the sidewall.

51. The bottle of claim 50 wherein a pair of opposing inclined walls extend from the groove along side edges of the panel generally radially outwardly to side edges of the fields and to the groove.