Multi-functional base for a plastic, wide-mouth, blow-molded container

Abstract

A blow molded container having a multi-functional base which enables use of the container in both hot-fill operations and pasteurization/retort operations and enables efficient vertical stacking of like containers. To this end, a portion of the base is capable of flexing upwardly and/or downwardly in response to variations in pressures in a filled and sealed container. Structurally, the base has a continuous or discontinuous concave outer annular wall forming a continuous or discontinuous standing ring and an inner annular wall functioning as a flex panel. The inner annular wall connects outwardly to a plurality of radial webs extending at an elevation above the standing ring and connects inwardly to a central dimple. Preferably, the inner periphery of the annular wall is heat-set and biaxially oriented.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of co-pending U.S. Non-Provisional Application No. 10/124,734 filed on Apr. 17, 2002 which claims the benefit of priority of U.S. Provisional Patent Application No. 60/284,795 filed on Apr. 19, 2001.

FIELD OF THE INVENTION

[0002] The present invention relates to a base for a wide mouth blow-molded plastic container, and more particularly, the present invention relates to a multi-functional base structure which enables use of the container in hot-fill, as well as pasteurization/retort processing.

BACKGROUND OF THE INVENTION

[0003] Plastic blow-molded containers, particularly those molded of PET, have been utilized in hot fill applications where the container is filled with a liquid product heated to a temperature in excess of 180° F. (82° C.), capped immediately after filling, and allowed to cool to ambient temperatures. Plastic blow-molded containers have also been utilized in pasteurization/retort processes where a filled and sealed container is subjected to thermal processing and is then cooled to ambient temperatures. In both cases, the containers are typically provided with vacuum absorption panels to accommodate volumetric changes in the container as the contents of the sealed container are heated and/or as the contents cool within the sealed container.

[0004] U.S. Pat. No. 6,439,413 issued to Prevot et al. and assigned to Graham Packaging Company, L.P. discloses a hot-fillable and retortable plastic wide-mouth blow-molded container having a sidewall with a pair of flex panels.

[0005] Co-pending U.S. patent application Ser. No. 10/129,885 filed on May 10, 2002 is the U.S. national phase of International Application No. PCT/US00/31834, is assigned to Graham Packaging Company, L.P., and discloses a pasteurizable wide-mouth container having a novel base.

[0006] Other plastic wide-mouth containers having paneled sidewalls are disclosed in U.S. Pat. Nos.: 5,887,739 issued to Prevot et al.; 5,261,544 issued to Weaver, Jr.; and 5,092,474 issued to Leigner. A pasteurizable plastic container having paneled sidewalls and a narrow neck finish is disclosed by U.S. Pat. No. 5,908,128 issued to Krishnakumar et al.

[0007] Containers having non-paneled sidewalls and yieldable endwall structures are disclosed in U.S. Pat. Nos. 4,642,968, 4,667,454 and 4,880,129 issued to McHenry et al.; 5,217,737 issued to Gygax et al.; 5,234,126 issued to Jonas et al.; 4,381,061 issued to Cerny et al.; 4,125,632 issued to Vosti et al.; and 3,409,167 issued to Blanchard. The above cited U.S. patents disclose containers having various base structures.

[0008] The structure of a so-called footed base is disclosed, in general, in U.S. Pat. Nos.: 4,355,728 issued to Yoshino et al.; 5,713,480 issued to Petre et al.; 3,727,783 issued to Carmichael; 4,318,489 issued to Snyder et al.; 5,133,468 issued to Brunson et al.; 5,024,340 issued to Alberghini et al.; 3,935,955 issued to Das; 4,892,205, 4,867,323 and Re. 35,140 issued to Powers et al.; and 5,785,197 issued to Slat.

[0009] U.S. Pat. No. 4,321,483 issued to Dechenne et al. discloses a base having slightly angled annular surface and a central conical projection; and U.S. Pat. No. 4,386,701 issued to Galer discloses a blow molded plastic drum having a base which is designed to stack efficiently with the lid of a like drum.

[0010] While the above referenced containers and base structures may function satisfactorily for their intended purposes, there is a need for a plastic, wide-mouth, blow-molded container which is particularly suited for packaging a variety of viscous and other food products and which has a novel base structure that enables the container to be utilized in hot-fill and pasteurization processes. The base structure should be capable of accommodating increased internal pressure experienced during pasteurization; capable of accommodating vacuum formed in the sealed container during cool down; capable of resisting unwanted inversion or like deformation; and capable of efficient stacking with like containers.

OBJECTS OF THE INVENTION

[0011] With the foregoing in mind, a primary object of the present invention is to provide a commercially satisfactory wide-mouth blow-molded container that can be utilized in hot-fill applications as well as pasteurization, or retort, applications for packaging fluent, viscous and solid food products.

[0012] Another object of the present invention is to provide a base structure capable of accommodating an increase in internal container pressure when the sealed container is subjected to thermal treatment and capable of accommodating vacuum during cool down.

[0013] Still another object of the present invention is to provide a hot-fillable and pasteurizable container having a base which accommodates changes in internal pressure and volume and which resists unwanted inversion and other deformation.

[0014] A further object of the present invention is to provide a structure for a wide-mouth plastic container which can be efficiently stacked, one on top of the other, with like containers and which can be produced by means of high speed manufacturing equipment in an economical manner that ensures consistent quality and performance.

SUMMARY OF THE INVENTION

[0015] More specifically, the present invention provides a blow molded plastic container having a base with a continuous or discontinuous concave outer annular wall having an outer portion and an inner portion forming a standing ring therebetween. The base also includes an inner annular wall that extends within the outer annular wall and above the standing ring. The inner periphery of the inner annular wall is made of blow molded plastic material that is heat-set and biaxially-oriented and connects to an anti-inverting central dimple. Functionally, the inner annular wall is capable of flexing upwardly and downwardly in response to variations in pressures in a filled and sealed container without undergoing unwanted permanent deformation. In addition, preferably a shoulder extends radially inward on the inner portion of the outer annular wall above a level of the standing ring to facilitate vertical stacking of containers having like bases.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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:

[0017] FIG. 1 is a perspective view of a container having a base embodying the present invention;

[0018] FIG. 2 is an elevational view of the container illustrated in FIG. 1;

[0019] FIG. 3 is bottom plan view of the base illustrated in FIG. 1;

[0020] FIG. 4 is a cross-sectional view of the base taken along line 4--4 of FIG. 3;

[0021] FIG. 5 is a cross-sectional view of the base taken along line 5--5 of FIG. 2 and illustrates a pair of containers in a stacked arrangement;

[0022] FIG. 6 is a perspective view of a second embodiment of a container having a base embodying the present invention;

[0023] FIG. 7 is an elevational view of the container illustrated in FIG. 6;

[0024] FIG. 8 is bottom plan view of the base illustrated in FIG. 6;

[0025] FIG. 9 is a cross-sectional view of the base taken along line 9--9 of FIG. 8; and

[0026] FIG. 10 is a cross-sectional view of the base taken along line 10-- 10 of FIG. 7 and illustrates a pair of containers in a stacked arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027] The present invention provides containers, 10 and 100, which are particularly suited for use as a jar for packaging food products. For example, the containers 10 and 100 can be used to package fluent or semi-fluent food products such as applesauce, spaghetti sauce, relishes, sauerkraut, baby foods, and the like. They can also be used to package a solid food product suspended in a liquid brine, such as pickles. Thus, the containers, 10 and 100, can be utilized for packaging various food products and can withstand various fill and treatment operations, as will be discussed.

[0028] The embodiment of the present invention illustrated in FIGS. 1-5 is a container 10 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.

[0029] 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.

[0030] Structurally, the base 12 includes a continuous or discontinuous concave outer annular wall 28. In the illustrated embodiment of base 12, concave outer annular wall 28 is discontinuous and provides a plurality of spaced-apart, arcuate supports 30 adjacent the outer periphery 32 of the base 12. Four supports 30 are utilized in the illustrated embodiment; however, two, three, five or more supports 30 could also be utilized. Yet another alternative includes providing concave outer annular wall 28 as a continuous structure that forms a continuous standing ring.

[0031] 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. Thus, a discontinuous support ring of the container 10 is provided in the illustrated embodiment. Alternatively, as discussed above, a continuous support ring can be provided.

[0032] An inner annular wall 40 extends within the concave outer annular wall 28 and may, or may not, be slightly inclined relative to the horizontal. For instance, the inclined inner annular wall 40 can extend upwardly and inwardly at an angle “A” relative to the horizontal as it extends from its outer periphery 42 to its inner periphery 44. By way of 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.

[0033] The outer periphery 42 of the inner annular wall 40 merges with the inner wall portion 36 and, in the illustrated embodiment, 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. A base having a continuous outer annular wall would not include webs 46.

[0034] The inner periphery 44 of the inner annular wall 40 merges into an anti-inverting dome 48 which projects upwardly into the container 10. In the illustrated embodiment, the inner annular wall 40 and anti-inverting dome 48 merge via an annular hinge 50. As illustrated in FIG. 4, the anti-inverting dome 48 has a conical lower portion 52 adjacent hinge 50 and a convex upper portion 54.

[0035] 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. 4 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. 4. 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.

[0036] 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.

[0037] 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. 5, 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 10b.

[0038] 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.

[0039] A second embodiment of the of the present invention is illustrated in FIGS. 6-10 as container 100. Container 100 has a base 112, a sidewall 114, and a wide-mouth threaded finish 116 which projects from the upper end of the sidewall 114 via a shoulder 118. Preferably, as illustrated, upper and lower label bumpers, 120 and 122, are located adjacent the shoulder 114 and base 112, respectfully, and outline a substantially cylindrical label area 124 on the sidewall 114. In addition, preferably the sidewall 114 has a series of circumferential grooves 126 which reinforce the sidewall 114 and resist paneling, dents and other unwanted deformation of the sidewall 114.

[0040] The container 100 is multi-functional since it can be utilized in hot-fill as well as pasteurization/retort processing. To accomplish this objective, the base 112 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 112 flexes downwardly in a controlled manner and to a desired extent when pressure within the filled and sealed container is elevated, and the base 112 flexes upwardly in a controlled manner and to a desired extent when a vacuum develops within the filled and sealed container.

[0041] Structurally, the base 112 includes a concave outer annular wall 128 that is either continuous or discontinuous. In the illustrated embodiment, base 112 has 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. In an additional contemplated embodiment of the present invention, the concave outer annular wall 128 is provided as a continuous structure that forms a continuous support ring.

[0042] An inner annular wall 140 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.

[0043] 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, 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.

[0044] The base 112 of container 100 is specifically designed to provide greater flexural movement than base 12 of container 10 discussed above so that it can be utilized in processes that require relatively high hot-fill and/or pasteurization/retort temperatures. 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 larger than the inner annular wall 40 of the container 10, despite the containers 10 and 100 being of the same given size. To this end, the diameter, size, or extent of the central dimple 148 is reduced relative to the size of dome 48, and the inner diameter of the arcuate supports 130 is increased relative to that of arcuate supports 30.

[0045] The relatively large flat provided by inner annular wall 140 provides greater flexure; however, it also is more prone to “roll out”, ie. becoming permanently deformed in an outwardly projecting position when its contents are hot-filled or heated at relatively high temperatures. 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.

[0046] 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 bi-axially oriented 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. 6. 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 is bi-axially oriented and capable of being heat-set by heated surfaces of a blow mold.

[0047] Thus, the inner annular wall 140 flexes downwardly when the container is filled, capped and subjected to an increase in pressure within the container, but is prevented from complete inversion and failure due to the reinforcement ribs 150 formed in the dimple 148 which travel with the inner annular wall 40 but substantially maintain a constant shape regardless of the internal pressure experienced within the container.

[0048] Another feature of the base 112 of the present invention is that each inner wall portion 136 of the arcuate supports 130 has 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. 10, an upper container 100a is 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 “Pa” 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.

[0049] 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 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.

[0050] Preferably, the containers 10 and 100 are blow molded from an injection molded preform made of PET, PEN or blends thereof or is extrusion blow molded of PP. In addition, the containers 10 and 100 may be multilayered including a layer of gas barrier material or a layer of scrap material. Preferably, the finishes of the containers are threaded, blow molded, and severed from an accommodation feature formed thereabove.

[0051] The above described containers 10 and 100 are capable of use, for instance, in hot-fill operations having fill temperatures up to about 205° F. As explained above, preferably container 100 having base 112 is utilized when temperatures approach or exceed the 205° F temperature level. The containers can also be utilized in pasteurization processes wherein a cold solid product, such as pickles, is combined within the container with mildly heated brine at 120 to 140° F. 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.

[0052] 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.

Claims

1. A container comprising a blow molded plastic body having an integrally formed base with a central annular wall having an inner periphery connecting to an anti-inverting central dimple that projects from said inner periphery of said inner annular wall, said inner periphery being made of blow molded plastic material that is heat-set and biaxially-oriented, said inner annular wall of said base flexing upwardly and downwardly in response to variations in pressures within the container, when capped and filled, without undergoing unwanted permanent deformation.

2. A container according to claim 1, wherein said central dimple includes an indented, substantially-circular surface having indented hollow ribs formed therein.

3. A container according to claim 1, further comprising a plurality of spaced-apart, radially-extending, indented ribs on said base where said inner periphery of said central annular wall interconnects to said central dimple.

4. A container according to claim 3, wherein said base has a concave outer annular wall with an outer portion and an inner portion forming a container standing surface therebetween.

5. A container according to claim 4, wherein said concave outer annular wall is continuous.

6. A container according to claim 4, wherein said concave outer annular wall is discontinuous.

7. A container according to claim 4, wherein said inner portion of said outer annular wall has a support ridge formed therein above a level of said container standing surface to facilitate vertical stacking of containers having like bases.

8. A container according to claim 4, wherein said standing ring has a diameter of at least about 3.7 inches, and said inner periphery of said central annular wall is less than about 1.25 inches.

9. A blow-molded plastic container comprising an integrally formed base made of blow molded plastic material, said base having:

a discontinuous concave outer annular wall having an outer portion and an inner portion forming a standing ring therebetween;

an inner annular wall extending inwardly from said inner portion of said outer annular wall, said inner annular wall having an inner periphery and an outer periphery, said outer periphery having a plurality of radial webs extending outwardly at an elevation above said standing ring, and said inner periphery being made of blow molded plastic material that is heat-set and biaxially-oriented; and

an anti-inverting central dimple projecting upwardly from said inner periphery of said inner annular wall;

said inner annular wall being deflectable upwardly and downwardly in response to variations in pressures within the container, when capped and filled, without undergoing unwanted permanent deformation below the level of the standing ring.

10. A container according to claim 9, further comprising a plurality of spaced-apart, radially-extending, indented ribs on said base where said inner periphery of said inner annular wall interconnects to said central dimple.

11. A container according to claim 9, wherein said central dimple has a plurality of spaced-apart, radially-extending, indented ribs formed therein.

12. A container according to claim 9, further comprising a shoulder extending radially inward on said inner portion of said outer annular wall above a level of said standing ring to facilitate vertical stacking of containers having like bases.

13. A container according to claim 9, further comprising a thin-walled body extending upwardly from said outer annular wall and having a blown wide-mouth threaded finish at an upper end of said body.

14. A container according to claim 9, wherein said container and base is made of PET, wherein said standing ring has a diameter of at least about 3.7 inches, and said inner periphery of said inner annular wall is less than about 1.25 inches and said outer periphery of said inner annular wall is at least about 2.5 inches.

15. A container, comprising:

a blow molded plastic body having a circular base, a cylindrical sidewall projecting from said base, and a threaded finish opposite said base;

said base having a discontinuous concave outer annular wall with an outer portion and an inner portion forming a container standing surface therebetween, said outer portion connecting to said sidewall;

said base having an inner annular wall extending inwardly from said inner portion of said outer annular wall, said inner annular wall having an inner periphery and an outer. periphery, said outer periphery connecting to a plurality of radial webs which extend at an elevation above said container standing surface and which connect to said sidewall, and said inner periphery being made of blow molded plastic material that is heat-set and biaxially-oriented;

said base having an anti-inverting central dimple projecting upwardly from said inner periphery of said inner annular wall; and

said inner annular wall of said base flexing upwardly and downwardly in response to variations in pressures in the container without undergoing unwanted permanent deformation.

16. A container according to claim 15, further comprising a plurality of spaced-apart, radially-extending, indented ribs on said base where said inner periphery of said inner annular wall interconnects to said central dimple.

17. A container according to claim 16, wherein said inner portion of said outer annular wall has a support ridge formed therein above a level of said container standing surface to facilitate vertical stacking of containers having like bases.

18. A container according to claim 17, further comprising a cap for sealing said finish, said cap having a top surface with an outer edge and said outer edge of said cap being engagable with said support ridge formed on a container having a like base to facilitate vertical stacking.

19. A container according to claim 17, wherein said cylindrical sidewall provides a cylindrical label panel having a plurality of longitudinally spaced circumferential reinforcement grooves and outlined by an upper and lower label bumper.

20. A container according to claim 17, wherein said body is made of PET, said discontinuous outer annular wall of said base forms four identical, equally spaced apart, arcuate supports, and said arcuate extent of each arcuate support is greater than an arcuate extent of each radial web.