Method Of Processing A Plastic Container Including A Multi-Functional Base

Abstract

A container can have a body with an integrally formed base attached to the body. The base includes a concave annular wall extending from the container sidewall to a standing surface, and an inner wall extending from the standing surface to a substantially flat inner annular wall. The inner annular wall is recessed in the base and is substantially perpendicular to the container sidewall. The inner annular wall includes a centrally located dimple. The dimple includes a plurality of spaced apart and radially extending indented ribs. One or more of the ribs extend radially into a brace that tapers to meet the inner annular wall.

Claims

1. A method comprising: providing a container comprising a body having an integrally formed base attached thereto, said base including: a concave annular wall extending from a sidewall of the container to a standing surface; an inner wall extending from the standing surface to a substantially flat inner annular wall that is substantially perpendicular to the sidewall; and a dimple centrally located within said inner annular wall and comprising a plurality of spaced apart radially extending indented ribs, each of said ribs comprising a brace extending radially from said dimple and tapering toward said inner annular wall, the tapering braces each including a wide portion and a narrow portion narrower than the wide portion, the wide portion being arranged at a junction with the inner annular wall, wherein said inner annular wall of said base has a position to which it flexes upwardly and has another position to which it flexes downwardly in response to variations in pressures within the container, when filled and sealed, without undergoing unwanted permanent deformation; filling the container; sealing the container; and upwardly and downwardly flexing the inner annular wall of the filled container above a standing ring, the flexing being in response to variations in pressures within the container, when filled and sealed.

2. A method of processing a plastic container, comprising: (a) providing a plastic container having an upper portion including a finish, a sidewall, a lower portion including a base defining a standing surface, and a substantially transversely-oriented pressure panel located in the base; (b) introducing heated liquid contents into the plastic container with the pressure panel located in an outwardly-inclined position entirely between the standing surface and the upper portion; (c) capping the plastic container; and (d) moving the pressure panel to an inwardly-inclined position entirely between the standing surface and the upper portion.

3. The method of claim 2, further comprising the step of moving the pressure panel from the inwardly-inclined position to the outwardly-inclined position prior to the step (b).

4. The method of claim 3, further comprising the step of blow molding the plastic container with the pressure panel in the inwardly-inclined position.

5. The method of claim 2, further comprising the step of applying mechanical force to the pressure panel to move the pressure panel from the outwardly-inclined position to the inwardly-inclined position.

6. The method of claim 2, further comprising the step of cooling the plastic container and liquid contents prior to the step (d).

7. The method of claim 2, wherein the step (d) occurs as a result of internal vacuum formed within the plastic container due to shrinkage of the liquid contents.

8. A method of blow molding a plastic container, comprising: (a) enclosing a softened polymer material within a blow mold defining a mold cavity, the blow mold comprising at least first and second side mold portions and a base mold portion; (b) inflating the polymer material within the blow mold to at least partially conform the polymer material to the blow mold cavity; and (c) displacing the base mold portion with respect to the first and second side mold portions to form a transverse pressure panel deeply set within a base portion of the plastic container.

9. The method of claim 8, further comprising the step of opening the blow mold to release the plastic container.

10. The method of claim 8, wherein the step (a) comprises enclosing a container preform within the blow mold.

11. The method of claim 10, further comprising the step of stretching the container preform with a stretch rod.

12. The method of claim 8, wherein the base portion comprises a standing surface defining a standing plane, and the pressure panel is located between the standing plane and an upper portion of the plastic container.

13. The method of claim 8, wherein the mold cavity defines a longitudinal axis of the plastic container, and the step (c) comprises displacing the base mold portion substantially along the longitudinal axis.

14. The method of claim 8, further comprising the step of substantially completely conforming the polymer material to the mold cavity prior to the step (c).

15. A method of processing a bottle, comprising: blowing the bottle in an as-blown position; filling the bottle with a hot liquid; moving a pressure panel down from the as-blown position; capping and sealing the filled bottle filled with the hot liquid; creating a vacuum force in the filled bottle by cooling the hot liquid; in response to the vacuum force, the pressure panel moving up into the interior of the bottle, the moving up causing a reduction in the vacuum force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing and other objects, features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

[0023] FIG. 1 is a perspective view of a container having a base according to an embodiment of the present invention;

[0024] FIG. 2 is an elevational view of the container illustrated in FIG. 1;

[0025] FIG. 3 is bottom plan view of the base illustrated in FIG. 1;

[0026] FIG. 4 is a cross-sectional view of the base taken along line IV-IV of FIG. 3;

[0027] FIG. 5 is a cross-sectional view of the base taken along line V-V of FIG. 2 and illustrates a pair of containers in a stacked arrangement;

[0028] FIG. 6 is a perspective view of a container having a base according to another embodiment of the invention;

[0029] FIG. 7 is a bottom view of the base according to the embodiment illustrated in FIG. 6;

[0030] FIG. 8 is a cross-section of the base of FIG. 6 taken along the VIII-VIII line of FIG. 7;

[0031] FIG. 9 is a cross-section of the base of FIG. 6 taken along the line IX-IX of FIG. 7;

[0032] FIG. 10 is a perspective view of a container having a base embodying the present invention;

[0033] FIG. 11 is an elevational view of the container illustrated in FIG. 10;

[0034] FIG. 12 is bottom plan view of the base illustrated in FIG. 10;

[0035] FIG. 13 is a cross-sectional view of the base taken along line 4-4 of FIG. 12; and

[0036] FIG. 14 is a cross-sectional view of the base taken along line 5-5 of FIG. 11 and illustrates a pair of containers in a stacked arrangement.

DETAILED DESCRIPTION OF THE INVENTION

[0037] An embodiment of the present invention is illustrated in FIGS. 1-5 as container 100. Container 100 has a base 112, a tubular sidewall 114, and a wide-mouth threaded finish 116 which projects from the upper end of the sidewall 114 via a shoulder 118. In the illustrated embodiment, upper and lower label bumpers, 120 and 122, are located adjacent the shoulder 118 and base 112, respectfully, and outline a substantially cylindrical label area 124 on the sidewall 114. Containers according to the invention can have cross-sectional shapes other than circular. In addition, the sidewall 114 can have a series of circumferential grooves 126 which reinforce the sidewall 114 and resist paneling, dents and other unwanted deformation of the sidewall 114.

[0038] The container 100 is multi-functional since it can be utilized in hot-fill as well as pasteurization and retort processing. To accomplish this objective, the base 112 has a structure which is capable of accommodating elevated internal container pressure experienced during pasteurization or retort processing, and which is capable of accommodating reduced container volume and pressure experienced upon cool down of a filled and sealed container after hot-fill, pasteurization or retort processing. To this end, the base 112 can flex downwardly in a controlled manner and to a desired extent when pressure within the filled and sealed container is elevated, and the base 112 can flex upwardly in a controlled manner and to a desired extent when a vacuum develops within the filled and sealed container.

[0039] Structurally, the base 112 includes a concave outer annular wall 128 that is either continuous or discontinuous. FIGS. 1-5 illustrate an embodiment of the base 112 having a discontinuous concave outer annular wall 128 that provides a plurality of spaced-apart, arcuate supports 130 adjacent the outer periphery 132 of the base 112. Each support 130 has an outer wall portion 134 that extends upwardly toward the lower label bumper 122 and an inner wall portion 136 that extends upwardly and inwardly into the remaining base structure as will be discussed. A standing surface 138 is formed at the juncture of each outer and inner wall portions, 134 and 136, thereby forming a discontinuous support ring of the container 100. FIGS. 6-9 illustrate an embodiment of a base 212 having a continuous concave outer annular wall 228 that forms a continuous standing surface 238, as described more fully below.

[0040] An inner annular wall 140 of base 112 extends within the concave outer annular wall 128. The inner annular wall 140 has an outer periphery 142 and an inner periphery 144. The outer periphery 142 of the inner annular wall 140 merges with the inner wall portion 136 of each of the supports 130 and, in the illustrated embodiment, with a plurality of spaced-apart, horizontally-disposed, radial webs 146 located adjacent the outer periphery 132 of the base 112. Each of the webs 146 extends between the supports 130 and connects to the container sidewall 114 at an elevation above the horizontal plane P extending through the standing surface 138. In an embodiment of the present invention in which the concave outer annular wall 128 is continuous, webs 146 are not provided. The inner periphery 144 of the inner annular wall 140 merges into an anti-inverting central dimple 148.

[0041] The inner annular wall 140 functions as a flex panel. To this end, when the internal pressure increases within a filled and sealed container, the inner annular wall 140 flexes downwardly to accommodate the increased pressure and to prevent the sidewall 114 of the container 100 from undergoing unwanted permanent distortion. In addition, the inner annular wall 140 flexes upwardly to relieve vacuum when the contents of a hot filled and capped container, or a filled, capped and subsequently pasteurized container, cool to ambient. Thus, when the sealed container and contents cool to ambient temperature, the sidewall 114 is substantially unchanged from its as-formed shape and is capable of neatly supporting a wrap-around label without unwanted voids or the like beneath the label. In addition, the sidewall 114 resists ovalization and the base 112 provides a level seating surface which is not subject to rocking or the like.

[0042] The base 112 of container 100 is specifically designed to provide flexural movement. Increasing flexure of the base 112 is accomplished by providing a larger circular flat between the dimple 148 and the arcuate supports 130. Thus, the inner annular wall 140 of container 100 is relatively large compared to other containers of a similar size. To this end, the diameter, size, or extent of the central dimple 148 is reduced and the inner diameter of the arcuate supports 130 is increased relative to prior art container.

[0043] The relatively large flat surface provided by inner annular wall 140 provides greater flexure; however, it can also be more prone to roll out, i.e. becoming permanently deformed in an outwardly projecting position when its contents are hot-filled or heated at relatively high temperatures, such as those encountered during pasteurization or retort processing. This is because an amorphous ring of material is created at the interconnection of the inner periphery 144 of the inner annular wall 140 and the dimple 148 due to the reduced size of the dimple 148. This ring of unoriented, non heat-set material provides a weakened area that permits the base to roll out when filled and sealed with contents at high temperatures.

[0044] The base 112 of the present invention overcomes the roll out problem by providing a series of spaced-apart, radially-extending, hollow, indented ribs 150 in the dimple 148 where the inner periphery 144 of the inner annular wall 140 interconnects to the central dimple 148. The structure provided by the ribs 150 causes the material in this region to be stretched during blow molding of the container 100 so that the ring of material adjacent the interconnection of the dimple 148 and inner annular wall 140 is both heat-set and the extent of biaxial orientation increased to structurally reinforce the base and prevent roll out of the base 112. If desired, the dimple 148 can be indented to a given extent into the container 100 to provide additional stretching, and the total number of ribs 150 can be three or more, such as six as illustrated in FIG. 1. In addition, the shape and size of the ribs can vary as long as the blow molded plastic material forming the base at the interconnection of the dimple 148 and inner annular wall 140 has sufficiently increased biaxial orientation and is heat-set by heated surfaces of a blow mold.

[0045] Thus, the inner annular wall 140 flexes downwardly when the container is filled, capped and subjected to an increase in pressure within the container. However, complete inversion and failure is prevented by the reinforcement ribs 150 formed in the dimple 148, which travel with the inner annular wall 140. The ribs 150 and dimple 148 maintain a substantially constant shape regardless of the internal pressure experienced within the container, due to the increase in density and stiffness resulting from the increased orientation.

[0046] Another feature of the base 112 of the present invention is that each inner wall portion 136 of the arcuate supports 130 can have an arcuate shoulder, or support ridge, 156 formed therein and spaced in elevation from both the support surfaces 138 and the inner annular wall 140 to facilitate vertical stacking of like containers 100. For example, as illustrated FIG. 5, an upper container 100a can be stacked on a lower container 100b. The support ridge 156 in the base 112a of the upper container 100a seats on the outer edge 158 of the upper surface 160 of the lid 162 of the lower container 100b such that the horizontal plane P.sub.a extending through the standing surfaces 138a of the upper container 100a extends a spaced distance beneath the top surface 160 of the lid 162 of the lower container 100b.

[0047] By way of example, and not by way of limitation, the container 100 according to the present invention preferably has a height H of about 5.8 inches, a container outermost diameter D of about 4.2 inches, and can contain a capacity of about 32 fluid ounces. The discontinuous standing ring formed by the standing surfaces 38 has a diameter of about 3.7 inches, and the inner annular wall 140 of the base 112 has an inner periphery 144 with a diameter of less than about 1.25 inches and an outer periphery 142 with a diameter of at least about 2.5 inches. The radial webs 146 are uniformly spaced apart and separate each support 130 such that each support 130 is at least about 0.8 radians. In addition, each support 130 has a larger arcuate extent than that of each radial web 146.

[0048] FIGS. 6-9 illustrate a second embodiment of a base 212 that may be used on a container 200 according to the present invention. Other than the base 212, the container 200 can be the same as or different from container 100. Accordingly, the last two digits in reference numerals used to designate features of the container 200 are the same as the reference numerals that are used to designate the related features in container 100. For example, the container 200 can include a threaded finish 216 that can be the same as the threaded finish 116 of the first embodiment, and can accommodate a closure 262 having complementary threads. Similarly, the shoulder 218, upper bumper 220, circumferential grooves 226, label area 224, and sidewall 214 can be structurally similar to the corresponding features of the first embodiment.

[0049] The second embodiment of the base 212 includes a continuous concave outer annular sidewall 228. The outer portion 228 of the annular sidewall curves from the sidewall 214 toward the center of the container 200 to form a continuous standing surface 238. The standing surface 238 is formed as a continuous, circular surface. Further, the transition from the outer annular sidewall 228 to the standing surface 238 is gradual and continuous. An inner portion 236 of the outer annular sidewall extends from the standing surface 238 to a substantially flat inner annular wall 240. The outer periphery 242 of the inner annular wall 240 forms a continuous ring around the inner annular wall 240.

[0050] Approximately centrally located on the inner annular wall 240 is a dimple 248. Extending outwardly from the dimple 248 are a series of ribs 250. The dimple 248 of this embodiment can be substantially the same size as the dimple 148 in the first embodiment 100, or can be slightly larger. The ribs 250 of the second embodiment extend outwardly to form a series of radially placed braces 270, which taper to an elevation that meets the flat inner annular wall 240 before, near, or the outer periphery 242 of the inner annular wall. In the illustrated embodiment, the ribs 250 first extend outward from the dimple at a similar depth to the inner portion 272 of the dimple to a rib wall 274, where there is a relatively abrupt change in depth toward the inner annular wall 240. The rib wall 274 extends up to a brace ledge 276 which slopes towards the surface of the inner annular wall 240. The brace ledge 276 can meet the surface of the inner annular wall 240 at or before the outer periphery 242. The sidewall of the brace 278 extends upward from the brace ledge 276 to the surface of the inner annular wall 240. The brace sidewall 278 meets the inner annular wall 240 at a periphery of the brace 270. The sidewall of the brace 278 can be substantially perpendicular to the inner annular wall 240 and the brace ledge 276.

[0051] The inner annular wall 240 in base 212 flexes in a manner analogous to the inner annular wall 140 of base 112. The radially spaced braces 270 further control flexure of the annular wall 240 in response to the reduced pressures that occur when the container cools down during hot-fill processing, and the reduced and increased pressures that occur during pasteurization and retort processing. The presence of the braces 270 allows greater flexure of the inner annular wall 240 within the concave outer annular wall 228 without allowing permanent deformation of the base. In addition, the presence of a continuous outer annular wall 228 is useful during rigorous pasteurization or retort conditions. Under such conditions, a discontinuous outer sidewall that has feet can have a tendency for the feet to pull in, causing the lower bumper to move into a square shape. By having a continuous standing surface 238 and a continuous outer annular sidewall 228, this tendency is reduced. Further, the presence of a continuous standing surface 238 alleviates any tendency for excessive base rollout.

[0052] The base structure described herein is illustrated without a support ridge 156 (see FIGS. 1-5) for stacking of containers. Such a ridge or shoulder can, however, be readily incorporated into a base 242 according to this second embodiment of the invention.

[0053] The base 212 according to the present invention is preferably crystallized to some extent as previously described in the first embodiment. Some degree of crystallinity and biaxial orientation is achieved normally during the blow molding process. Crystallization can also be promoted through heat setting of the container. For example, the walls and base of the mold can be held at an elevated temperature to promote crystallization. When the container is heat set at a temperature of about 180 F., the container sidewalls, base, dome, and threads can be typically crystallized to about 20%. This degree of crystallinity is typical for a blow molding process and does not represent a significant amount of heat setting or increased crystallinity or orientation, as compared with a typically prepared container. However, the properties of the base of the present invention can be advantageously enhanced by heat setting the container, and particularly the base, at ever higher temperatures. Such temperatures can be, for example, greater than 250 F. and can be 325 F. or even higher. When these elevated heat set temperatures are utilized, crystallinity can be increased to greater than 20% or 25% or more. One drawback of increasing crystallinity and biaxial orientation in a plastic container is that this process introduces opacity into the normally clear material. However, unlike bases in prior art containers designed for use in pasteurization and retort processes, which can require a crystallinity of 30% or more, utilizing crystallinities of as low as 22-25% with a base structure according to the present invention can achieve significant structural integrity, while maintaining the substantial clarity of a base that is preferred by manufacturers, packagers and consumers of such pasteurized commodities. Crystallinities of 30% or greater that are frequently utilized in prior container to achieve significant structural integrity can cause undesirable opacity in the base region.

[0054] Bases formed with configurations according to the present invention provide a more appealing structure to consumers, packagers and manufacturers for other reasons, as well. For example, when switching from the use of glass to plastic in packaging such pasteurizable commodities, design changes cause undesirable changes in the internal container configuration. Typically, in order to withstand the rigors of pasteurization or retort processing, prior containers have included a base formed with a large central push-up, as is used in typical plastic containers used in hot-fill processes. This push-up limits the volume of material that can be placed in the container in the internal region between the push-up and the sidewalls. This can be particularly problematic when solid products, for example, pickles, are packaged. The presence of narrow channels which are formed between the sidewall and large base push-up in the internal space of a typical blow molded container, can limit the volume into which solid materials can be placed. That is, such designs create dead space within the container that can be filled by liquid, but not by the solid product. In traditional glass containers, a relatively flat bottom can be formed which allows solids to be packed throughout the vertical and radial extent of the container. Prior art plastic containers that have been utilized to withstand the pasteurization and retort conditions have used similar internal geometry, which creates dead space.

[0055] According to the present invention, and particularly according to the second embodiment described herein, the configuration of the base can reduce the amount of dead space and be much more similar to traditionally used glass containers. For example, the substantially flat inner annular wall 240 can extend to a substantial outward extent toward the edge of the container. By using a base configuration according to the present invention, the inner diameter of the standing surface, i.e. the pushed-up region of the base D.sub.1, as shown in FIG. 9, can be a relatively large portion of the container diameter D.sub.2. According to the present invention, the ratio of the container diameter D.sub.2 to the pushed-up diameter D.sub.1 can be less than 1.5:1.0 and even 1.3:1.0 or lower. Stated differently, the diameter of the container D.sub.2 can be less than 50% larger than, or as little as about 30% larger than, the diameter of D.sub.1 of the pushed-up region. In cases where the container is not round, this corresponds to a projected volume of the sidewall region less than 70% greater than the projected area of the push-up region.

[0056] By way of example, and not by way of limitation, the container 200 according to the present invention can have dimensions similar to those of the container 100. For example, the container can have a height of about 5.8 inches, an outer most diameter D.sub.2 of about 3.8 inches, and can contain a capacity of about 32 fluid ounces. The pushed-up region of the base can have a diameter D.sub.1 of about 3.1 inches. The brace 270 can have a brace ledge 276 that extends out about 0.6 inches from the dimple 248. The distance between opposite rib walls 274 can be about 1.2 inches, while the distance across the dimple 248 in the region between ribs can be about 0.9 inches.

[0057] The containers 100 and 200 can be blow molded from an injection molded preform made from, for example, PET, PEN or blends thereof, or can be extrusion blow molded plastic, for example, polypropylene (PP). In addition, the containers 100 and 200 can be multilayered, including a layer of gas barrier material or a layer of scrap material. Resins also include polyester resins modified to improve UV resistance, for example Heatwave CF246, available from Voridian (Kingsport, Tenn., U.S.A.). The finishes of the containers can be injection molded, i.e. the threaded portion can be formed as part of the preform, or can be blow molded and severed from an accommodation feature formed thereabove, as is known in the art.

[0058] The above described containers 100 and 200 are capable of use, for instance, in hot-fill operations having fill temperatures up to about 205 F. As explained above, containers 100 and 200 having base 112 and 212 can be utilized when processing temperatures approach or exceed 205 F. The containers can also be utilized in typical pasteurization processes used in the packaging art. In an exemplary process, a cold solid product, such as pickles, is combined with mildly heated brine at 120 to 140 F. within the container. After the container is capped, the filled container can be processed through a pasteurization tank, where temperatures approach about 212 F., so that the solid products in the sealed container are heated to approximately 175 F. for 15 minutes before the filled and sealed container is cooled to ambient temperature.

[0059] The present invention provides a container 10 which is particularly suited for use as a jar for packaging food products. For example, the container 10 can be used to package fluent or semi-fluent food products such as applesauce, spaghetti sauce, relishes, sauerkraut, baby foods, and the like. It can also be used to package a solid food product suspended in a liquid brine, such as pickles. Thus, the container 10 can be utilized for packaging various food products and can withstand various fill and treatment operations, as will be discussed.

[0060] As illustrated in FIG. 10, in one preferred embodiment of the present invention a container 10 is provided having a base 12, a substantially cylindrical sidewall 14, and a wide-mouth threaded finish 16 which projects from the upper end of the sidewall 14 via a shoulder 18. Preferably, as illustrated, upper and lower label bumpers, 20 and 22, are located adjacent the shoulder 14 and base 12, respectfully, and outline a substantially cylindrical label area 24 on the sidewall 14. Thus, a label (not shown) can be attached to, and extend completely around, the container sidewall 14. In addition, preferably the sidewall 14 has a series of circumferential grooves 26 which reinforce the cylindrical shape of the sidewall 14 and resist paneling, dents and other unwanted deformation of the sidewall 14.

[0061] The container 10 is multi-functional since it can be utilized in hot-fill as well as pasteurization/retort processing. To accomplish this objective, the base 12 has a structure which is capable of accommodating elevated internal container pressure experienced during pasteurization/retort processing and which is capable of accommodating reduced container volume experienced upon cool down of a filled and sealed container after hot-fill or pasteurization/retort processing. To this end, the base 12 flexes downwardly in a controlled manner and to a desired extent when pressure within the filled and sealed container is elevated, and the base 12 flexes upwardly in a controlled manner and to a desired extent when a vacuum develops within the filled and sealed container.

[0062] Structurally, the base 12 includes a discontinuous concave outer annular wall 28 which provides a plurality of spaced-apart, arcuate supports 30 adjacent the outer periphery 32 of the base 12. As illustrated, four supports 30 are utilized in the preferred embodiment; however, three, five or more supports 30 could also be utilized. Each support 30 has an outer wall portion 34 which extends upwardly toward the lower label bumper 22 and an inner wall portion 36 which extends upwardly and inwardly into the remaining base structure as will be discussed. A standing surface 38 is formed at the juncture of each outer and inner wall portions, 34 and 36, thereby forming a discontinuous support ring of the container 10.

[0063] An inner annular wall 40 extends within the discontinuous concave outer annular wall 28 and is preferably slightly inclined relative to the horizontal. Preferably, the inclined inner annular wall 40 extends upwardly and inwardly at an angle A relative to the horizontal as it extends from its outer periphery 42 to its inner periphery 44. For example, the inner annular wall 40 can incline at an angle A in a range of about 5 to about 6 relative to a horizontal plane P extending through the standing surfaces 38. Alternatively, the inner annular wall 40 can be formed substantially planar and parallel to a horizontal plane P extending through the standing surfaces 38.

[0064] The outer periphery 42 of the inner annular wall 40 merges with the inner wall portion 36 of each of the supports 30 and with a plurality of spaced-apart, horizontally-disposed, radial webs 46 located adjacent the outer periphery 32 of the base 12. Each of the webs 46 extends between the supports 30 and connects to the container sidewall 14 at an elevation above the horizontal plane P extending through the standing surfaces 38. The inner periphery 44 of the inner annular wall 40 merges into an anti-inverting dome 48 which projects upwardly into the container 10. Preferably, the inner annular wall 40 and anti-inverting dome 48 merge via an annular hinge 50. As illustrated in FIG. 13, the anti-inverting dome 48 has a conical lower portion 52 adjacent hinge 50 and a convex upper portion 54.

[0065] The inner annular wall 40 functions as a flex panel. To this end, when the internal pressure increases within a filled and sealed container, the inner annular wall 40 flexes downwardly as shown in dashed lines B in FIG. 13 to accommodate the increased pressure and prevent the sidewall 14 of the container 10 from undergoing unwanted permanent distortion. In addition, the inner annular wall 40 flexes upwardly to relieve vacuum when the contents of a hot filled and capped container, or a filled, capped and subsequently pasteurized container, cool to ambient. This is shown in dashed lines C in FIG. 13. Thus, when the sealed container and contents cool to ambient, the sidewall 14 is substantially cylindrical and unchanged from its as-formed shape and is capable of neatly supporting a wrap-around label without unwanted voids or the like beneath the label. In addition, the sidewall 14 resists ovalization and the base 12 provides a level seating surface which is not subject to rocking or the like.

[0066] The anti-inverting dome 48, the supports 30 and the radial webs 46 support the inner annular wall 40 and permit it to flex only within a desired range of movement as illustrated by dashed lines B and C. For instance, the inner annular wall 40 flexes downwardly due to an increase in pressure within the container, but is prevented from complete inversion and failure by the anti-inverting dome 48 which travels with the inner annular wall 40 but substantially maintains a constant shape regardless of the internal pressure experienced within the container.

[0067] Another feature of the base 12 of the present invention is that each inner wall portion 36 of the arcuate supports 30 has an arcuate shoulder, or support ridge, 56 formed therein and spaced in elevation from both the support surfaces 38 and the inner annular wall 40 to facilitate vertical stacking of like containers 10. For example, as illustrated FIG. 14, an upper container 10a is stacked on a lower container 10b. The support ridge 56 in the base 12a of the upper container 10a seats on the outer edge 58 of the upper surface 60 of the lid 62 of the lower container 10b such that the horizontal plane Pa extending through the standing surfaces 38a of the upper container 10a extends a spaced distance beneath the top surface 60 of the lid 62 of the lower container 10h.

[0068] By way of example, and not by way of limitation, the container 10 according to the present invention preferably has a height H of about 5.8 inches, a container outermost diameter D of about 4.2 inches, and contain a capacity of about 32 fluid ounces. The discontinuous standing ring formed by the standing surfaces 38 has a diameter of about 3.6 inches, and the inner annular wall 40 of the base 12 has an inner periphery 44 with a diameter of about 1.6 inches and an outer periphery 42 with a diameter of about 2.2 inches. The radial webs 46 are uniformly spaced apart and separate each support 30 such that each support 30 is at least about 0.8 radians. In addition, each support 30 has a slightly larger arcuate extent than that of each radial web 46.

[0069] Preferably, the container 10 is blow molded from an injection molded preform made of PET, PEN or blends thereof or is extrusion blow molded of PP. In addition, the container 10 may be multilayered including a layer of gas barrier material or a layer of scrap material. Preferably, the finish 16 of the container is threaded, blow molded, and severed from an accommodation feature formed thereabove.

[0070] The above described container 10 is capable of use in hot-fill operations having fill temperatures up to 205 F. It can also be utilized in pasteurization processes wherein a cold solid product, such as pickles, is combined within the container 10 with mildly heated brine at 120 to 140 F. After the container 10 is capped, the filled container can be processed through a pasteurization tank where temperatures approach about 212 F. so that the solid products in the sealed container are heated to approximately 175 F. for 15 minutes before the filled and sealed container is cooled to ambient temperature.

[0071] While preferred containers and base structures have been described in detail, various modifications, alterations and changes may be made without departing from the spirit and scope of the present invention as defined in the appended claims.