One-piece plastic container for carbonated beverages

Abstract: A one-piece plastic container for carbonated beverages with a footed base structure (7) to support the container in an upright position. The container is manufactured with a reduced amount of plastic material while maintaining performance, particularly stability. Stability is preserved when the container is empty and when filled. The upper portion of the base structure has a strap formation (17) between each circumferentially adjacent pair of feet (35) that is relatively stiff and which communicate at their outer ends with readily deformable areas (15). When the container is pressurized from the carbonated beverage the areas (15) easily deform and expand to avoid unwanted distortions that commonly occur in other footed container base structures and cause the strap formations (17) to apply an upwardly directed force to the central region (14) of the base structure.

Description: Background of the Invention This invention relates generally to a one piece plastic carbonated beverage container with a footed base structure; and particularly, a container of this type molded with a reduced amount of plastic material. These containers are usually, although not exclusively, made from a polyethylene terephthalate (PET) polyester material using a blow molding process that biaxially orients and sets its molecular structure. A major difficulty in a filled and sealed carbonated container is controlling and minimizing the distortion of the footed base structure from the pressure created by the carbonated beverage. Under normal conditions, this pressure can exceed 75 PSI (5bar). Uncontrolled distortion can lead to a variety of problems. One problem is poor container stability from a "rocker bottom" where the central region of the base bulges downwardly to a point where the supporting feet cannot simultaneously contact a supporting surface. In this case, the container is supported in a tilted somewhat unstable position by the central region and two of the feet. Another problem is container damage from buckling, creases, bumps and bulges in the feet and sidewall areas. In some cases, this can lead to structural damage from concentrated stresses; in other cases this can lead to an aesthetically unpleasing shape. Containers with concentrated stresses may burst if subjected to impact. Another problem is an inconsistent fill level line position created by an inconsistent expansion of the container, most of which occurs in the base structure area. Fill line position consistency is important to consumers in that consumers often believe a fill level below standard signifies an underfed or unsealed container. Also to be considered is that an unfilled container must be able to stand upright in the filling machinery. Containers that fall over during conveying will adversely affect the cost and efficiency of filling operations. Stability is improved with a wide stance of the feet of the base structure. Another consideration is maximization of the area of each foot pad in contact with the conveyor or other supporting surface. Small foot pads tend to become caught and fall over in the machinery. The prior art describes many examples of one piece plastic carbonated beverage containers with footed base structures. To achieve success, such containers depend on a relatively heavier container with substantial material thickness in the base structure area. The approach uses mass to resist distortion, but heavier containers tend to be costly to produce. When these containers are made with less material, many of the problems mentioned above occur. Those containers which tend to be lighter in weight tend to reduce the stance of the feet or reduce the area of each foot pad which often create stability problems before and after filing. GB-A-2 258 209 discloses a cylindrical shaped plastic bottle having a petaloid base structure. The petaloid feet or bulges of the base structure are separated by arcuate ribs that are arranged radially from central element of the base. EP-A-3 46 858 discloses a plastic bottle having a petaloid base structure. As seen in Figures 3 and 4 of this reference, between the footed structures of the base is a downwardly extending bottom wall generally defined by a series of outwardly and upwardly arcuate portions. As seen in Figure 6, the upper portions of the feet structures merge together and converge at the upper and outermost portions of the bottom wall. EP-A-671 331 discloses a carbonated beverage bottle having a petaloid base. Between each adjacent pair of feet is a radially extending strap or, as referred to in the reference, valley. The width of the valley decreases with increasing radial distance from the longitudinal axis of the bottle to a point of convergence on the bottle's outer diameter. The valley floor generally follows the hemispherical shape of the base and opens to an extended portion of the base shape laying radially outward of the feet. Upon initial pressurization of the bottle, the valley and extended portion cause deformation of the extended portion outwardly generally pivoting the valley about an area located approximately midway along the valley and resulting in the raising of the center portion of the base upward and away from a support surface upon which the bottle is standing. It is, therefore desirable to provide a footed carbonated beverage container of reduced material weight with a wide stance of the base structure feet and a large foot pad area while controlling and manipulating the expansion and distortion of the base from the beverage carbonation pressure so as not to adversely affect the consistency of fill line position, aesthetic appearance, stability, or to create excessive concentrated stresses. Summary of the Invention This invention provides a plastic container for carbonated beverages according to claim 1 which has a base structure extending downwardly from a generally tubular sidewall. The form of the base structure is developed from several shapes smoothly blended together. The shapes selected satisfy the need for stability when empty and when filled with a carbonated or other beverage and sealed. Pressure from the carbonation is expected to alter the container-as-molded-shape to a new and desirable container-as-filled-and-sealed-shape. In effect, the container-as-molded-shape influences or predetermines the form of the new container-as-filled-and-sealed-shape. In accordance with this invention, achieving a desired shape utilized the natural tendency of the blow molding process to create a slightly thicker container wall section in areas of the container mold which are contacted first by the expanding parison as it inflates. In the case of the container of this invention, the wall thickness of a central region of the base about a longitudinal axis, which blends to adjacent portions of a strap formation and which in turn extends substantially radially from the central region, tend to be thicker than the wall thickness of the container sidewall and the foot pad of each downwardly hollow projection. The container shape, upon pressurization, is predetermined to expand first in a region of the base structure adjacent to the merge point of the base to the sidewall. The strap formation which separates circumferentially adjacent pairs of support feet is itself partially separated by a downward extending wedge formation also partially positioned between the circumferentially adjacent pairs of feet. The forces acting on the strap are evenly distributed to the sidewall by this split and by adjacent areas. When viewing the container longitudinally, the preferred strap formation assumes a shape similar to a letter Y. The footed container of this invention is aesthetically pleasing, provides a stable wide stance support both before and after filling, meets other generally accepted industrial and consumer expectations, and is significantly lighter in weight than containers previously known. Brief Introduction to the Drawings Further advantages of the invention will become apparent to those skilled in the art from the following description, taken in connection with the accompanying drawings, in which: Figure 1 is a side elevational view of a prior art container; Figure 2 is a side elevational view of a container with a base structure of the present invention; Figure 3 is a bottom view of the container of Figure 2 illustrating five identical circumferentially spaced downwardly hollow foot projections of the base structure; Figure 4 is an enlarged elevational view of an area between a pair of downwardly hollow foot projections; Figure 5 is a sectional view as seen along line 5-5 of Figure 2; Figure 5a is a sectional view as seen along line 5-5 of Figure 2; Figure 6 is an elevational view of the base structure illustrated in phantom so as to better view a bottom wall from which the downwardly hollow foot projections project; Figure 7 is a bottom view similar to Figure 3 except that most shading detail is removed to better illustrate the position of section line 8-8; Figure 8 is an enlarged sectional view as seen along line 8-8 of Figure 7 illustrating a shape for the area between a pair of downwardly hollow foot projections; Figure 9 is an enlarged elevational view of a wedge formation between a pair of downwardly hollow foot projections essentially as seen in Figure 2, including an illustrated elemental shape as it generally appears to the eye; Figure 10 is an enlarged elevational view like Figure 9 of an alternative separated strap formation; Figure 11 is a partial side elevational view of an alternative configuration of the base of the present invention; Figure 12 is a sectional view as seen along line 12-12 of Figure 11; and Figure 13 is a graphical representation, at various levels of pressure within the container, of central region positions relative to the support foot pads. Detailed Description of the Invention With reference to the drawings, Figure 1 illustrates a shape of a typical one piece footed carbonated beverage container. Generally containers of this type have four broad regions, namely a neck finish (1), a shoulder portion (3), a sidewall portion (5), and a base structure (7). Typically the base structure (7) comprises three, five, or six hollow foot projections (8) which extend downwardly in a arc from the sidewall (5) to provide the support for the container. Between any pair of these foot projections (8) is a formation (10) which in the prior art is often referred to as a rib or a valley. This strap formation of the base structure extends radially outwardly and upwardly from a central region about a longitudinal axis (9) eventually blending with the sidewall (5) with a rounded point like shape (12). A nominal two liter container, for example, will often weight 55 grams or more. These prior art containers generally work well, but in applications where the amount of material or weight of the container is reduced, to minimize manufacturing cost, (for example reductions to 50 grams or 48 grams or less in a two liter sized container) distortions can occur from the beverage carbonation pressure that will greatly influence container stability, performance, and aesthetic appeal. These distortions can create unwanted surface buckling, creases, and bulges in areas in the foot projections (8), the in-between formations (10), near the rounded point (12), and in the central base region about axis (9). These distortions often concentrate structural stresses in these areas which in turn can lead to a container breach if subjected to impact. Typically, these containers are manufactured from a polyethylene terephthalate (PET) polyester plastic material using a blow molding process that biaxially orients and sets its molecular structure. Other materials such as polyethylene naphthalate (PEN) or some combination of terephthalate and naphthalate based materials can also be used. While these are the most likely choices, others may be considered as well. The plastic container of the invention has a base structure, when manufactured with a reduced amount of material, that allows controlled distortion to occur while alleviating the above mentioned problems. This container as shown in Figure 2 includes a neck finish (1) merging with a shoulder portion (3) which in turn smoothly merges with a sidewall portion (5) which in turn smoothly merges with a closed base structure (7). The container provides stable support when empty and when filled with a carbonated beverage and sealed. The base structure (7) permits controlled expansion to primarily occur in an upper circumferential region near the lower end of the side wall portion (5). The base structure (7) is created by extending downwardly and smoothly inwardly from the sidewall (5) a minimum of three hollow projections or legs (35) disposed about the longitudinal axis (9) terminating in substantially planar foot pads (11) which in turn contact a support surface, not illustrated, thereby providing support for the one piece container. Figure 3 is a bottom view of the base structure (7) of Figure 2. Separating each circumferentially adjacent pair of hollow projections (35) is a relatively stiff strap formation (13) which in turn divides to form separated strap formations (17). Together the strap formation (13) and the separated strap formations (17), when viewed longitudinally (Figure 2), assume a shape similar to a letter Y. In Figure 3, the shape and features of a hollow projection (35), a foot pad (11), a strap formation (13), a pair of separated diverging strap formations (17), is repeated five times and evenly disposed about the center of the container. Five supporting feet is the preferred embodiment of the invention, but those skilled in the art will recognize the invention is not limited to five. Also shown is a central region (14) of base structure (7). It can thus be seen that each strap formation (13) starts at the central region (14), and extends between a pair of hollow feet (35) in a radially outward and upward direction from the axis (9). The strap formation (13) is then divided into diverging strap formations (17) which extend upwardly through the area of the base above the legs (35) to positions adjacent the lower end of the sidewall portion (5) of the container. The area of the base structure (7), located generally between the diverging strap formations, sometimes referred to as a wedge formation (15), is readily expanded as shown in broken lines in Fig. 5, when the container is filled with a carbonated beverage. The strap formations (17) are relatively stiff and thus act to confine the expansion in the area between the straps (17). Preferably, the hollow feet (35) smoothly blend to the foot pads (11) with a substantially circular shaped boundary as shown in Figures 3 and 4. Distance A (Figure 3) is a distance from the center of the container to the sidewall (5). Distance B from the center of the container to the outer edge (21) of foot pad (11) is preferably 70 percent of distance A or greater. This positioning of the foot pads will provide the wide stance needed for improved stability. The substantially planar foot pad (11) shape (as shown in Figure 4) is the shape as manufactured. In combination with the wide stance, it contributes to the stability of the container in handling equipment before and during container filling. Once the container is filled with a carbonated beverage and sealed, the foot pad (11), in a controllable fashion, expands to assume a somewhat flat hemispheroidal shape (27) without creases or folds or other distortions which will detract from container stability. This is particularly true with the pad shape described above having a circular boundary. Turning to Figure 9, an enlarged segment of the base formation of the invention is illustrated. The wedge formation (15) merges from the sidewall portion (5) and is positioned circumferentially an equal distance from an adjacent pair of hollow projection (35). The strap formation (13) is separated by the wedge formation (15) to create separated strap formations (17) which in turn helps to distribute the forces of pressurization to the sidewall portion (5). Without this wedge formation (15) and separated strap formation (17), pressurization will concentrate forces in an area near the rounded point like shape (12) of prior art Figure 1. To the eye, the wedge formation (15) (Figure 9) preferably has a shape with a rounded inverted triangular character (41), particularly when considering an imaginary line (39) created by the division of the base structure (7) merging from the sidewall portion (5). Figure 6 illustrates a bottom wall (29) of the base structure (7). The hollow projections (35) and wedge formations (15) are represented with phantom lines to better illustrate the shape of the bottom wall (29). Bottom wall (29) is a foundation shape from which the hollow projections (35) and wedge formations (15) extend. Once extended little of the bottom wall (29) configuration remains; nevertheless, the bottom wall (29) configuration is an important element of the base structure configuration after the container is filled with a carbonated beverage and sealed. The bottom wall (29) is shaped from an inverted truncated conical section (31) with a side angle α smoothly merging with a radius R1 from the sidewall portion (5). Smoothly merging downwardly with radius R2 from the conical section (31) is a spherical segment (33) with radius R3. Radius R3 can be either less than, equal to, or greater than dimension A. The surface of conical section (31) is not tangential to the surface of spherical segment (33). Figures 7 and 8 illustrate a view of the strap formation (13). Figure 7 is a bottom view of the base structure identical to Figure 3 except that most contour lines depicting shape have been eliminated to better show section 8-8 location. Figure 8 is an enlarged partial cross sectional view of the strap formation (13) and its relationship to the bottom wall (29). The strap formation (13) is actually a transition zone with a radius between adjacent pairs of hollow projections (35) and in close proximity to the bottom wall (29). Point 37 is the only remaining portion of the strap formation (13) in common with the bottom wall (29) when viewed in Figures 7 and 8. In the base structure (7), point (37) becomes a locus of points as the strap formation (13) extends from the central region (14) to the corresponding separated strap formations (17). The locus of points (37) continues in the separated strap formations (17) to merge with the sidewall (5). Turning now to Figure 5, there is shown a cross sectional view of base structure (7) along line 5-5 in Figure 2. Details lying beyond the cross section taken are omitted for clarity. Likewise, the repeating features of the hollow projections (35), separated strap formations (17), and wedge formations (15) are not all numbered. A grouping of one set of these features, including two separated strap formations (17), is repeated five times, and each group is circumferentially evenly spaced. The cross sectional view clearly illustrates an inside surface (16) and an outside surface (18). Upon pressurization with a carbonated beverage, the circumferential region of the base structure as shown in Figure 5 easily expands to assume a smoother more rounded shape as shown by phantom line (19) representing a new position for the outside surface (18). The degree of smoothing is dependent on the amount of pressure applied by the beverage. In an extreme situation, the separated strap formations (17) will become difficult to detect and the wedge formation (15) will become a rounded bulge. It appears that this expansion allows a pivotal force to be applied to the relatively rigid strap formations (13) allowing the central region (14) to initially move upwardly relative to the support foot pads (11). As pressure quickly continues to build inside the container, the shoulder portion (3) and sidewall portion (5) expand slightly radially outward. The central region (14) returns to approximately its original position. The hollow projections (35) appear to thrust slightly outward in a somewhat radial direction while the strap formations (13) appear to flatten slightly. The foot pads (11) assume a slightly somewhat hemispheriodal shape while the base structure (7) provides a stable container support. Figure 13 is a graphical representation, at various levels of pressure within the container, of the position of central region (6, 14) relative to the support foot pads (4,11). The position of central region (6) of a tested prior art container (Figure 1) steadily decreases as pressure increases. The position of central region (14) of a tested container of this invention (Figure 2) initially increased before decreasing as pressure increases. At 5 bar (75 PSI), the pressure of a typical carbonated beverage container filled and sealed at room temperature, the central region (14, Figure 2) is at a position approximately equal to its position prior to filling. Figure 5a is a cross sectional view of base structure (7) along line 5a-5a in Figure 2 clearly illustrating strap formation (13) position relative to the hollow projections (35). Phantom line (20) represents the outer surface (18) of section 5-5 of Figure 5 and illustrates the separated strap formations (17) and wedge formation (15) in relationship to strap formation (13) and hollow projections (35). Figure 10 illustrates a modified form of the wedge formation (15) (Figure 9) and the separated strap formations (17), wherein two or more smaller wedge formations (15b) separate strap formation (13) into three or more separated strap formations (17). Figures 11 and 12 illustrate an alternative configuration of the base structure (7), wherein the strap formation (13) extending substantially radially from the central region (14) merges with a fan shaped formation or area (45) forms a section in common with the bottom wall (29) (Figure 6) resulting in a gentle radius as shown in Figure 12. Also shown are hollow projections (35) merging with a radius to the fan shaped strap formations (45). From the above description, it is seen that this invention provides a lightweight beverage container which can be made with a reduced amount of plastic. This objective is achieved by providing the container according to claim 1. The result is an improved container which is reliable in standing on a flat surface, is economical to manufacture, and which effectively accomodates expansion while resisting deformation when filled with a carbonated beverage. While the above description discloses the preferred embodiment of the invention, it will become apparent to those skilled in the art that modifications, and alterations may be made without deviating from the invention's scope as defined in the following claims.

Claims: A self standing blow molded polyester container for carbonated beverages, said container having a longitudinal axis (9) and a neck finish (1) integral with and terminating in a shoulder portion (3) which is integral with and terminates in a side wall portion (5) which is integral with terminates in a closed base structure (7); the shoulder portion, side wall portion and the base structure being biaxially oriented; and the base structure being of a form defining a plurality of equally spaced feet (35) disposed about the longitudinal axis whereby the container is self standing, circumferentially adjacent pairs of the feet (35) define, support, and are separated by, relatively stiff first strap formations (13) each extending substantially radially from a central region (14) of the base structure, centered on the longitudinal axis (9), to a relatively deformable area (15) of the base structure located radially outwardly of the feet and adjacent to said side wall portion, characterized in that: each said first strap formation (13) terminating at its radially outer end (26) in a pair of diverging second strap formations (17) separated by the deformable area (15) which can expand outwardly between the pair of diverging strap formations (17), each strap formation (13) and pair of diverging strap formations (17) forming a Y-shaped configuration, said deformable area (15) extending upwardly to a position adjacent the sidewall portion (5) of the container and being located between the pair of diverging second strap formations (17) whereby initial internal pressurization of the container will expand the deformable (15) area radially outwardly away from the longitudinal axis, which in turn moves the radially outer ends (13a) of the relatively stiff first strap formations (13) radially outwardly and upwardly away from the longitudinal axis, thereby pivoting the first strap formations (13) about their support by the feet and moving the radially inner ends of the first strap formations (13) generally upwardly toward the neck finish, thereby moving the central region (14) of the base along the longitudinal axis (9) toward the neck finish. The container according to claim 1 wherein said deformable area is a wedge shape bubble which projects radially outwardly from said container at a location between a circumferentially adjacent pair of said legs. The container according to claim 1 wherein said deformable area is of a fan shape. The container according to claim 2 wherein said wedge formation and the adjacent separated second strap formations separated by said wedge formation smoothly deform such that said wedge formation becomes a rounded bulge. The container according to claim 1 wherein five similar feet are evenly circumferentially disposed about said longitudinal axis.

Inventors: LANE MICHAEL T, LANE, MICHAEL T.
Applicants: HOOVER UNIVERSAL, HOOVER UNIVERSAL INC.
Application year: 1995
Main classification: B65D1
IPC codes: B65D1