Pasteurizable and hot-fillable blow molded plastic container

A blow molded plastic container for hot fill and pasteurization uses includes a main body portion that is shaped so as to be substantially rectangular in horizontal cross-section and a base portion. The base portion is shaped to define a generally rectangular standing ring and an elevated push-up portion that is positioned radially inward of the standing ring. The push-up portion includes a central region, an annular, substantially straight and substantially vertical rise portion that is positioned immediately radially inward of the standing ring and a plurality of radially oriented waves. Each of the waves extends radially outwardly from the central region to the vertical rise portion. The main body portion is shaped so as to have sidewall portions that are bounded by a plurality of vertically extending edge portions. In one embodiment, at least one of the vertically extending edge portions may have at least one inwardly extending gusset.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to blow molded plastic containers, and particularly blow molded plastic containers that are designed to accommodate the pressurization and vacuum forces that are inherent in the pasteurization and/or hot fill processes.

2. Description of the Related Technology

Many products that were previously packaged using glass containers are now being supplied in plastic containers, such as containers that are fabricated from polyesters such as polyethylene terephthalate (PET).

PET containers are typically manufactured using the stretch blow molding process. This involves the use of a preform that is injection molded into a shape that facilitates distribution of the plastic material within the preform into the desired final shape of the container. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it takes on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold.

The use of blow molded plastic containers for the purpose of packaging liquids that are processed by hot filling and/or pasteurization processes has been known for some time. The hot fill process involves filling the containers while the liquid product is at an elevated temperature, typically 68° C. to 96° C. (155° F.-205° F.) and usually about 85° C. (185° F.) in order to sterilize the container at the time of filling. Containers that are designed to withstand the hot fill process are known as “hot fill” or “heat set” containers. Such containers are typically designed with sidewalls that include one or more vacuum panels that are designed to flex due to the temperature changes and consequent volumetric expansion and contraction that takes place during processing.

Pasteurization subjects a container to greater internal pressures and volumetric changes than occurs with hot-fill processing. This is due to the higher processing temperatures, and, therefore, the greater volumetric expansion and contraction of the contained products and associated vapor.

Hot fill and pasteurizable containers must be designed to be strong enough in the areas outside of the vacuum panel regions so that the deformation that occurs as a result of the volumetric shrinkage of a product within the container is substantially limited to the portions of the container that are designed specifically to accommodate such shrinkage. Ideally, this is done while keeping the container as lightweight as possible, because PET resin is relatively expensive.

The sidewall portions of hot fill and pasteurizable containers must be designed to prevent excessive deformation, particularly in containers that are not designed to be substantially circular or round as viewed in horizontal cross-section. In addition, the base of such containers must be designed to be stable and to prevent excessive deformation. PET hot fill and pasteurizable containers typically have a modified champagne style base that defines an outer standing ring on which the container is designed to be supported when placed on a flat horizontal surface, and a central, elevated push-up region. The push-up region of such containers has a tendency to deform when the container is under pressure, which can cause the material near the standing ring to roll or deflect outwardly, thus compromising the stability of the base.

A need exists for an improved blow molded plastic container for use in hot fill and pasteurizable applications that has a sidewall and base portion that both remain relatively stable under various conditions of pressurization and temperature that occur during such processes.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an improved blow molded plastic container for use in hot fill and pasteurizable applications that has a sidewall and base portion that both remain relatively stable under various conditions of pressurization and temperature that occur during such processes.

In order to achieve the above and other objects of the invention, a blow molded plastic container according to a first aspect of the invention includes a main body portion that is shaped so as to be substantially rectangular in horizontal cross-section and a base portion. The base portion is shaped to define a generally rectangular standing ring and an elevated push-up portion that is positioned radially inward of the standing ring. The push-up portion includes a central region, an annular, substantially straight and substantially vertical rise portion that is positioned immediately radially inward of the standing ring and a plurality of radially oriented waves. Each of the waves extends radially outwardly from the central region to the vertical rise portion.

According to a second aspect of the invention, a blow molded plastic container includes a base portion; and a main body portion. The main body portion is shaped so as to have a plurality of sidewall portions that are bounded by a plurality of vertically extending edge portions. At least one of the vertically extending edge portions has at least one inwardly extending gusset defined therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular toFIG. 1, a blow molded plastic container10is constructed and arranged to be pasteurizable and/or adapted to be used for packaging liquid products at elevated temperatures according to the well-known hot-fill process.

Blow molded plastic container10is preferably fabricated from polyethylene terephthalate, commonly known by the acronym PET, using a conventional blowmolding process. It preferably includes a main body portion12, a threaded nipple portion13that is provided with one or more helical threads for receiving a threaded lid, a base portion14and a shoulder portion15that is unitary with the threaded nipple portion13and the main body portion12.

The main body portion12is preferably shaped so as to be substantially rectangular in horizontal cross-section, and more preferably so as to be substantially square in horizontal cross-section.

Main body portion12includes four sidewall panels53and four vertically extending edge portions54. Each of the sidewall panels53preferably has a plurality of inwardly extending support ribs or grooves55defined therein for strengthening the sidewall panels53against inward and outward deflection that might otherwise occur as a result of temperature-induced pressure changes within the container10during the hot fill or pasteurization process. The inwardly extending support ribs or grooves55are in the preferred embodiment provided within a generally oval region57that is defined in the sidewall53. Preferably, each of the support ribs55is oriented so as to be substantially horizontal.

As is best shown inFIG. 3, each of the inwardly extending support ribs or grooves55further preferably has a depth DRthat is within a range of 0.050 inch to about 0.2 inch.

Referring briefly toFIG. 4, base portion14is shaped so as to define a generally rectangular and, more preferably, a generally square rectangular standing ring16having rounded corners on which the container10is adapted to be supported on an underlying flat horizontal surface such as a table or refrigerator shelf. Base portion14further includes an elevated push-up portion18that is positioned radially inward of the standing ring16. The elevated push-up portion18has a bottom wall portion that is shaped to define a central region20that includes a gate structure and that is substantially centered with respect to the elevated push-up portion18and the generally rectangular standing ring16.

The base portion14also preferably includes an annular, substantially straight vertical rise portion22, best shown inFIG. 3, that is positioned immediately radially inward of the standing ring16. The vertical rise portion22preferably extends for a vertical height HRfrom the bottom of the standing ring16that is preferably within a range of about 0.036 inch to about 0.2 inch.

According to one particularly advantageous feature of the invention, base portion14also includes a plurality of radially oriented waves24,26,28,30,32,34,36, best shown inFIG. 4, that extend radially outwardly from the central region20to the vertical rise portion22. Each of the radially oriented waves24,26,28,30,32,34,36includes a peak portion42that is preferably convexly radiused to extend downwardly and a trough portion44that is preferably concavely radiused so as to extend upwardly. A first cross-sectional view showing a plurality of the radially oriented waves and their respective peak and trough portions42,44at a location that is adjacent to the central region20is provided inFIG. 5. A second cross sectional view showing a plurality of the radially oriented waves in the respective peak and trough portions42,44at a location that is adjacent to the vertical rise portion22is shown inFIG. 6.

The generally rectangular standing ring16has four corner portions46,48,50,52that are preferably constructed so as to be slightly rounded. Each of the corner portions46,48,50,52is in the preferred embodiment radially aligned with a peak portion42of a corresponding wave. This facilitates efficient material distribution into the areas closest to the corner portions46,48,50,52as well as optimizing the structural reinforcement of the base portion14.

The peak portion42of each respective radially oriented wave24,26,28,30,32,34,36defines a radially oriented axis. Each of the waves24,26,28,30,32,34also defines a first transverse mean radius of curvature R1, shown inFIG. 5, at a first location that is shown inFIG. 4. Each of the waves further defines a second transverse mean radius of curvature R2, shown inFIG. 6, at a second location that is shown inFIG. 4. The second location is positioned so as to be radially outward from the first location. The second transverse mean radius of curvature R2is preferably greater than the first transverse mean radius of curvature R1, meaning that the peak portions of the waves tend to increase in both amplitude and width in proportion to the distance from the central region20of the bottom portion16.

Likewise, the trough portion44of each of the waves also defines a radially oriented axis, and each of the waves defines a first trough transverse mean radius of curvature R3, shown inFIG. 5, at the first location that is shown inFIG. 4. Each of the waves further defines a second trough transverse mean radius of curvature R4, shown inFIG. 6, at the second location that is shown inFIG. 4. The second location is positioned so as to be radially outward from the first location. The second transverse mean radius of curvature R4is preferably greater than the first transverse mean radius of curvature R3, meaning that the trough portions of the waves also tend to increase in amplitude and width in proportion to the distance from the central region20of the bottom portion16.

Preferably, both the trough portions44and the peak portions42are shaped so as to subtend a substantially constant angle along their respective lengths from the central region20to the vertical rise portion22.

The waves24,26,28,30,32,34are preferably symmetrically arranged about the central region20, meaning that each of the waves has a diametrically opposed counterpart wave positioned immediately and symmetrically opposite the central region20.

Preferably, at least four waves are provided. More preferably, at least six waves are provided. In the preferred embodiment, eight waves are provided. More than eight waves could also be provided within the scope of the invention.

A blow molded plastic container60that is constructed according to a second embodiment of the invention is shown inFIGS. 7-9. Container60is substantially identical to the container10described above, except that it is also provided with additional sidewall reinforcement in the vertically extending corners or posts, as will be described in greater detail below. It is also constructed and arranged to be used in high temperature and pressure applications such as pasteurization and hot-fill processing. It includes a main body portion62that is preferably rectangular and more preferably substantially square as viewed in horizontal cross-section.

The main body portion62is shaped so as to have a plurality of the sidewall portions70that are bounded by a corresponding plurality of vertically extending edge portions64that are slightly rounded and that provide rigidity to the main body portion62.

Container60further includes a base portion66that is constructed identically to the base portion14in the above described embodiment, a neck portion71and a threaded nipple portion73that is provided with external threading so as to receive a threaded lid. Container60further has a base portion75that is constructed identically to the base portion of the previously described embodiment.

Each of the sidewall portions70preferably has at least one inwardly extending support rib72defined therein that are constructed identically to the inwardly extending support ribs55described above with reference to the first embodiment. Preferably, a plurality of support ribs72are defined in each of the sidewall portions70, and each of the support ribs72are oriented so as to be substantially horizontal.

According to one advantageous feature of this aspect of the invention, at least one of the vertically extending edge portions64has at least one inwardly extending gusset68defined therein. Preferably, a plurality of and more preferably each of the vertically extending edge portions64includes at least one gusset68. Preferably, each of the vertically extending edge portions64has more than one gusset68defined therein. The gussets68provide enhanced structural support to the container60that permits relative lightweighting of the container while maintaining the strength of the container.

As is shown in the cross-sectional depiction that is provided inFIG. 9, each of the gussets68is in the preferred embodiment characterizsed by a concave groove67that is defined in the sidewall of the main body portion62. Specifically, the groove67is defined in the vertically extending edge portion64and preferably extends along an axis that forms substantially equal angles A with respective planes in which the adjacent sidewall portions70reside.

The groove67has a depth DG, which is preferably within a range of about 0.125 inch to about 0.500 inch. Groove67further is concavely radiused at a mean radius of curvature RG that is preferably within a range of about 0.0625 inch to about 0.250 inch.

The inwardly extending gussets68are in the preferred embodiment not disposed in the same horizontal plane as any of the support ribs72.