Patent Application
20110011825
1. Field of the Invention
This invention relates generally to the field of plastic containers, and more particularly to plastic containers that are designed to accommodate volumetric expansion and contraction such as that inherent to the hot-fill packaging process or to packaging applications where internal pressurization is anticipated.
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.
Hot fill containers are designed to be used with the conventional hot fill process in which a liquid or semi-solid product such as fruit juice, sauce, salsa, jelly or fruit salad is introduced into the container while warm or hot, as appropriate, for sanitary packaging of the product. After filling, such containers undergo significant volumetric shrinkage as a result of the cooling of the product within the sealed container. Hot fill type containers accordingly must be designed to have the capability of accommodating such shrinkage. Typically this has been done by incorporating one or more vacuum panels into the side wall of the container that are designed to flex inwardly as the volume of the product within the container decreases as a result of cooling.
Typically, the vacuum panel regions of conventional hot fill containers are characterized by having surfaces that are designed to deflect inwardly when the product within the sealed container undergoes shrinkage. In some instances, an inflexible island may be defined in the middle of the vacuum panel in order to provide support for an adhesive label that may be placed over the container. Grippability for the consumer is also an important consideration in the design of many containers.
The amount of volumetric contraction, also referred to as vacuum uptake, that can be provided by a conventional vacuum panel is limited by the size of the panel. The design of such containers is often influenced by the aesthetic preferences of manufacturers, which in some instances can limit the size of the vacuum panels to the extent that makes it difficult or impossible to achieve the necessary vacuum uptake capacity.
A need therefore exists for an improved vacuum panel configuration that achieves a maximal amount of vacuum uptake capacity in relation to the size of the vacuum panel.
Accordingly, it is an objection of the invention to provide an improved vacuum panel configuration that achieves a maximal amount of vacuum uptake capacity in relation to the size of the vacuum panel.
In order to achieve the above and other objects of the invention, a plastic container according to a first aspect of the invention that is adapted for adjustment to internal volumetric changes includes a container body defining an internal space. The container body has at least one flexible panel defined therein that includes an outer flexible panel portion and an inner flexible panel portion. The outer flexible panel portion has a shape when a pressure equilibrium exists between the internal space and ambient external pressure, and is further constructed and arranged to assume a more concave shape when a sufficient underpressure exists in the internal space. The inner flexible panel portion is located within the outer flexible panel portion, and is constructed and arranged to flex relative to the outer flexible panel portion in order to accommodate internal pressure changes within the container body.
A plastic container that is adapted for adjustment to internal volumetric changes, according to a second aspect of the invention includes a container body defining an internal space. The container body has at least one flexible panel defined therein that includes an outer flexible panel portion and an inner flexible panel portion. The inner flexible panel portion is located within the outer flexible panel portion, and an entire boundary between said outer flexible panel portion and said inner flexible panel portion is curved
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.
Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to
Container 10 includes a container body 12, which is preferably fabricated out of a material such as polyethylene terephthalate (PET) using a conventional stretch blow molding process. Container body 12 defines a longitudinal axis 42 and preferably includes a threaded finish portion 14 that defines an opening that is in communication with an internal space 28 that is defined within the container body 12. Finish portion 14 is adapted to receive a conventional closure (not shown) in order to seal the container 10 after filling by the manufacturer and between uses by the consumer. Container body 12 further preferably includes a neck or shoulder portion 16, a main body portion 18 and a bottom portion 20.
The container body 12 and in particular the main body portion 18 is molded so as to have a thin sidewall 22. The portion of the sidewall 22 that defines the main body portion 18 is shaped so that the outermost surfaces thereof are substantially cylindrical. The sidewall 22 is preferably configured and shaped so as to have at least one flexible panel 26 defined therein. In the preferred embodiment that is shown in
Sidewall 22 further defines a first sidewall portion 30 on a rear side of the container 10, which is provided with a plurality of concave ribs or grooves 32. A second sidewall portion 34 is similarly provided on a front side of the container 10, which is likewise provided with a plurality of concave ribs or grooves 36. The presence of the ribs or grooves 32, 36 on the respective first and second sidewall portions 26, 28 provides rigidity to a degree that prevents any substantial flexure of either sidewall portion 26, 28 as a result of the magnitude of pressure differential between the internal space 28 and ambient pressure that is expected to occur during the filling process or in subsequent handling of the container 10 by the manufacturer or the consumer.
Each of the flexible panels 26, 28 preferably includes an outer flexible panel portion 38 that has a shape that is flat, convex or concave in the unstressed position wherein a pressure equilibrium exists between the internal space 28 and ambient external pressure. In other words, the outer flexible panel portion 38 may be substantially flat, concave or convex under pressure equilibrium conditions. Preferably, however, the outer flexible panel portion 38 is flat or convex in the unstressed position. The outer flexible panel portion 38 is further constructed and arranged to increase in concavity when a sufficient underpressure exists in the internal space 28. In the preferred embodiment, it assumes a concave shape when a sufficient underpressure exists in the internal space 28. This underpressure, expressed as a difference between the internal and external pressures, is preferably within a range of about 0.5 psi to about 10.0 psi, and more preferably within a range of about 1.0 psi to about 6.0 psi.
Each of the flexible panels 26, 28 preferably also includes an inner flexible panel portion 40 that is located within the outer flexible panel portion 38 and defines a boundary 42 with respect thereto. The entire boundary 42 between the outer flexible panel portion 38 and the inner flexible panel portion 40 is preferably curved as viewed in side elevation. In the embodiment shown in
The inner flexible panel portion 40 is constructed and arranged to flex relative to the outer flexible panel portion 38 and the rest of the container 10 in order to accommodate internal pressure changes within the container body 10. More specifically, the inner flexible panel portion 40 preferably extends radially outwardly with respect to the outer flexible panel portion 38. In the preferred embodiment it has a relatively smooth, convex shape as viewed both along a longitudinal plane and along a transverse plane when it is in the unstressed position in which internal pressure is substantially equal to external pressure. As shown in
The inner flexible panel portion 40 defines a first surface area, and the outer flexible panel portion 38 defines a second surface area. A ratio of the first surface area to the second surface area is preferably within a range of about 0.5 to about 8.0. More preferably, this ratio is within a range of about 1.0 to about 6.0.
The inner and outer flexible panel portions 40, 38 accordingly work in tandem to permit more space-efficient vacuum uptake in a hot-fill type container than could be achieved using a single flat panel of comparable size.
In an alternative embodiment in which the invention is utilized to provide for the uptake of positive pressurization within the container, the inner flexible panel portion could be configured so that it is concave under equilibrium conditions, and flexes to a substantially flat shape or inverts or to a convex shape when a sufficient magnitude of positive internal pressurization is achieved.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
