Base structure for a container

A base structure for a blow-molded container having a sidewall is provided. The base structure comprises a support heel having an outer portion and an inner portion, the outer portion merging with the container sidewall. An inner projecting portion merges with the inner portion of the support heel. The inner projecting portion is inclined at an angle of at least about 50 degrees.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a base structure and more particularly to a base structure for a blow molded container with enhanced structural integrity and simplified geometry.

2. Related Art

Many products are sold to the consuming public in plastic containers such as are shown in U.S. Pat. Nos. 5,005,716 (Eberle); 4,108,324 (Krishnakumer et al); and 4,134,510 (Chang). The design of plastic containers must take into account the container's structural integrity, the manufacturing cost to mass produce the container, and the aesthetic appearance of the container to the eye of the consumer.

A hot-fillable plastic container must be structurally sound to withstand various forces relating to the so-called “hot-fill” process. Moreover, it must withstand rough handling during transportation to the ultimate consumer. A “hot-fill” process is the procedure by which containers are filled with a substance at a high temperature after which the containers are capped. As the substance cools within the container, stresses and strains develop in the container due to changes in the volume of the contents. Containers that store products under pressure, such as carbonated beverages, also experience pressure changes due to changes in ambient temperature. A commercially satisfactory container structure must not only withstand these forces from a structural viewpoint, but must also present an aesthetically pleasing appearance to the ultimate consumer.

The price of many products sold to the consuming public is affected to an extent by the cost of packaging. With plastic containers, the cost of manufacturing a container is affected by the cost of plastic composing the container. Therefore, if the amount of plastic in a container can be reduced, the cost of manufacturing the container can be reduced commensurately. However, in achieving this goal it is known that the thinner the walls and base of the container become, the greater the need to utilize imaginative designs to provide a container that is commercially acceptable.

The desire to decrease the amount of plastics used in a container has resulted in the development of different techniques to design containers that have structural integrity with minimal use of plastic. It is known that shape and location of structural elements such as ribs, hinges, panels, and the like can affect the container's overall structural integrity. While various structural elements molded in the side panel and base structure can afford structural integrity, they must also be visually appealing to the consumer and not impede the removal of a product from the container.

Krishnakumer et al. ('324) illustrate a rounded container base structure which employs various structural elements molded into the base which enhances structural integrity. This base design has a series of radially extending ribs which allow the base structure to withstand a variety of applied forces and which minimizes the use of plastic.

Eberle ('716) disclose a round base structure having a central concavity and a convex heel. The heel surrounds the concavity and merges therewith and with the container sidewall. A plurality of hollow convex ribs, distributed in a symmetrical array, interrupt the outer surface of the concavity and merge smoothly therewith, each rib extending longitudinally in the direction of the heel and downwardly from an inner portion of the concavity. The wall of the bottom structure generally decreases in thickness progressively from the innermost point of the concavity to the sidewall. The structure allows the base to withstand the various stresses and strains applied to the container and also minimizes the use of plastic.

Chang ('510) show a round base which employs a series of circumferential ribs in combination with radial ribs to provide the desired degree of structural integrity. The radial ribs intersect all of the circumferential ribs. The various ribs are solid.

Accordingly, as described above, prior base structures for blow molded containers usually include horizontal or vertical annular sections or ribs', to provide stiffness and increase structural support. These additional support structures create crevices and recesses in the interior of the container. When the container is used to store a viscous substance, such as jelly, jam, preserves or heavy syrup, the viscous substance may become trapped in these crevices and recesses. In these instances, a consumer may have difficulty accessing and removing the substance from the container.

Although the aforementioned containers and base structures may function satisfactorily for their intended purposes, there remains a continuing need for a blow-molded plastic container having a base structure which has a simplified geometry for facilitating removal of a substance from the container, while enhancing container structural integrity. Also, these base structures need to be aesthetically pleasing and be capable of being manufactured in conventional high speed equipment.

BRIEF SUMMARY OF THE INVENTION

In an exemplary embodiment of the invention, a base structure for a blow-molded container having a sidewall is provided. The base structure comprises a support heel having an outer portion and an inner portion, the outer portion merging with the container sidewall. An inner projecting portion merges with the inner portion of the support heel. The inner projecting portion is pushed up towards the body and is inclined at an angle of at least about 50 degrees

In another embodiment of the invention, a container comprises a hollow body portion having a longitudinal axis and a top portion with a finish extending upwardly from the body portion. An enclosed base portion includes an outer wall merging with the body portion opposite from the top portion and an inner wall merging with the outer wall to form a support surface. The inner wall includes a smooth inclined surface projecting inwardly towards the body portion and forming an interior angle of at least about 40 degrees with respect to a plane perpendicular to the longitudinal axis.

In another embodiment, a base structure for a container having a sidewall is provided The base structure comprises a support heel having an outer portion and an inner portion. The outer portion merges with the container sidewall. An inner projecting portion merges with the inner portion of the support heel. The inner projecting portion comprises a truncated cone, the cone being formed at an angle adapted to minimize a diameter of an amorphous ring of material formed therein.

Further objectives and advantages, as well as the structure and function of preferred embodiments will become apparent from a consideration of the description, drawings, and examples.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. All references cited herein are incorporated by reference as if each had been individually incorporated.

A preferred embodiment of the invention is discussed in detail below. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention.

Referring now to the drawings,FIG. 1illustrates a blow-molded plastic container1such as may be used in the sale of jelly, jam and preserves. Such containers can typically be designed to contain liquid volumes of a one-half gallon, 32 ounces, or the like. The container1comprises a base4for supporting the container1. The container1has a longitudinal axis100when the container1is standing upright on its base4. A hollow body6extends upwardly from the base4.

A top portion8finishes upwardly from the body6and may include a threaded neck12for filling and dispensing. Neck12also is sealable with a cap (not shown). The preferred container further comprises a shoulder11located below neck12and above body6. The body6is defined by roughly rectangular sides14that connect shoulder11and base4and has a rectangular cross-section. Of course, the body may have other shapes. The sides14of the preferred container may include at least one label mounting area. A label or labels can be applied to one or more of the label mounting areas using methods that are well known to those skilled in the art, including shrink wrap labeling and adhesive methods. As applied, the label extends either around the entire body of the container or extends over the entirety or a portion of the label mounting area.

The container1is preferably a pressure-adjustable container, in particular a ‘hot-fill’ container that is adapted to be filled with a substance at a temperature above room temperature. The container1may be formed in a blow mold and may be produced from a polyester or other plastic material, such as a heat set polyethylene terephthalate (PET). The cap (not shown) seals the container and confines the substance inside the container.

When used in a hot-fill processing, the container is filled with a substance at an elevated temperature. The cap is then installed on the container neck. As the temperature of the substance and air decreases to ambient temperatures, its volume decreases. The container and its base structure must react to the reduction in volume and accommodate the stresses and strains while remaining structurally sound. Moreover, the base must also be capable of withstanding various other forces, such as changes in internal pressure, and the usual handling forces.

The base structure according to embodiments of the present invention is shaped to withstand these various forces. The base structure reduces the need for plastic, yet still enhances the overall structural integrity of the container. Moreover, the base structure has a simplified geometry that allows for easy removal of the substance from the container. To this end, as seen inFIG. 2, the base structure according to an exemplary embodiment has an annular support heel18. The support heel18allows the container1to be supported erect on a horizontal surface. The support heel18is preferably rounded and forms an annular line of contact with the horizontal surface (not shown).

The annular support heel18has an inner and an outer portion,20and22, respectively. The outer portion22merges with the container's sidewall14. The inner portion20of the annular support heel18has an upwardly inclined surface24that forms an inner projecting portion25. The support heel18surrounds the inner projecting portion25.

The inner projecting portion25may comprise an inverted cone as shown inFIGS. 2 and 3. Inclined surface24forms walls26of the inverted cone. Walls26are substantially smooth and preferably do not include ribs, recesses or other structural elements formed therein. Walls26of the cone are formed in a much stepper angle and are raised up deeper into the container than is done on most traditional push-up bases. This increased height can allow the material used to form the inner projecting portion25to stretch down into the base and support heel18.

An inclination angle of the inner projecting portion25is selected to minimize an amorphous ring that inherently appears therein. After a hot fill process, the amorphous ring tends to roll out. However, the increased height and steeper angle of the inverted cone prohibit roll out past the support heel18of the container.

The inner projecting portion25is preferably inset from the support heel18of the container1. For example, the inverted cone25shown inFIG. 3is inset a distance D1from the support heel18. The amount of inset can depend upon the size of the container, the angle of inclination of the inverted cone, and other production factors. The inset distance D1between the walls26of the inverted cone and the support heel18of the container1can be utilized to facilitate the stacking of containers on top of each other. This area can be adapted to receive an exterior surface of a cap of a container. For example, as shown inFIG. 4, at least one concentric ring can be formed between the inner projecting portion25and the support heel18. In the embodiment illustrated, two concentric rings27A,27B are provided. The concentric rings27A,27B typically surround the inner projecting portion25and are also inset with respect to the support heel18. Here ring27A is inset a distance D2from support heel18and ring27B is inset a distance D3from support heel18. Ring27A is formed around ring27B. The concentric rings can have different heights, widths, etc. and can be adapted to receive and mate with the external surface of the cap that is used to seal the container. Accordingly, sealed, capped containers can be stacked on top of each other for easy storage and shipping.

A more detailed view of the base is shown inFIG. 2, which is a cross-section of the base. The inner portion20transitions at an inset from the support heel18into the inclined surface24. The inclined surface24projects inwardly towards the body6of the container1to form inner projecting portion25. The inner projecting portion25is adapted to minimize an amorphous ring of material that inherently forms therein. It has been determined experimentally that forming a portion of the base pushed up towards the hollow body6at an inclination angle of about 40 degrees or more minimizes the amorphous ring. In the embodiment illustrated inFIG. 4, the inclined surface24forms an inverted cone as the inner projecting portion25. However, the inner projecting portion25may take other shapes, for example, a pyramid shape.

In the embodiment shown inFIG. 2, a vertex of the inverted cone extends towards the hollow body6of the container1and a frustum of the cone is arranged in the vicinity of a plane of the support heel18. The inner projecting portion25preferably has a height H of about 0.2 inches or more as measured from the annular line of contact of the container with a horizontal support surface (not shown). Here, the inverted cone has a height of about 0.85 inches. The particular height of the inner projecting portion is dependent upon the preform used and how it distributes material in the base, the fill temperatures and other processing conditions. The extent to which the inner projecting portion25projects towards the body6may also contribute to minimizing the size of the amorphous ring and preventing roll out.

The vertex of the cone terminates in a plateau32. The plateau32is typically circular and in this embodiment has a diameter of about 0.4 inches. The plateau32may have a substantially flat top surface34. However, a dimple is typically present in the top surface34of the plateau32. The dimple in the illustrated embodiment is arcuate with a radius of about 0.375 inches. A button formed from excess material is typically present on a bottom surface36of the plateau32, opposite from the dimple. The inner projecting portion25is usually centered around the longitudinal axis100of the container.

The frustum of the cone opens downwardly away from the body6of the container1. In this embodiment, the opening of the frustum of the cone is circular and has a diameter of about 1.7 inches. The frustum may merge with a concentric ring formed in the base4or with the inner portion20of the support heel18.

The inclined surface24forms the sides of the cone and extend between the vertex and the frustum. As mention above, the inclined surface24of the inner projecting portion25is inclined at an angle selected to minimize the size of an amorphous ring of material present therein. The angle is preferably substantially constant along the length of the inclined surface. This interior angle α is measured with respect to a plane that is perpendicular to the longitudinal access of the container and inside the frustum of the cone, as shown in FIG.4. The inclined surface24is preferably inclined at an angle greater than about 40 degrees, and preferably greater than about 50 degrees. A cross-section of the inclined surface24is substantially linear.

The inclined surface24includes an interior surface28facing towards the interior of the container1an outer surface30facing outside of the container1. Preferably, at least the interior surface28is substantially smooth, that is, the interior surface28should not include any ribs, recesses, or other structural elements. The exterior surface30of the inclined surface24is also preferably smooth. Thus, the inner projecting portion25does not include and ribs or other structural elements. This helps to minimize the amount of plastic used to form the base and to simplify the production process. Also, eliminating as much geometry on the interior surfaces of the container as possible aids in removal of a substance from the container. Of course, both the interior and exterior surfaces28,30may include minor surface imperfections and defects that do not have a significant effect on the smoothness of their surfaces.

Accordingly, a base structure for a blow molded container is provided. The base structure comprises a push up portion which does not include any ribs or other structural supports. The geometry of the base structure is simplified and can facilitate the removal of substance from the container. The structure of the push up eliminates unnecessary geometry while still maintaining the structural integrity of the base. Additionally, by eliminating the need for ribs or additional structural members in the base push up, the amount of material needed to form the base structure is reduced and the manufacturing process of the container is simplified.

The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the present invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. For example, the dimensions described above related to a specific embodiment of the invention. Other shapes and sizes of the inner projecting portion are possible within the scope of the invention. It is therefore to be understood that, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.