Patent Application
20130153531
1. Field of the Invention
This invention relates generally to the field of blow molded plastic containers, and more particularly to containers that are suitable for use with food or beverage products that are packaged using the hot fill process.
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 lightweight, inexpensive, recyclable and can be economically manufactured in large quantities. PET therefore possesses excellent characteristics for containers, but PET resin is relatively expensive. Accordingly, a PET container design that reduces the amount of material that is used without sacrificing performance will provide a significant competitive advantage within the packaging industry.
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.
PET containers are particularly common for use in packaging beverages such as juices using what is known in the industry as the hot-fill process. This involves filling the containers while the liquid product is at an elevated temperature, typically 68° C.-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 process are known as “hot fill” or “heat set” containers.
Hot fill 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. In addition, since filled containers are often stacked on top of one another for transportation and distribution, the sidewall of such containers must be designed to have sufficient column strength in order to endure a predetermined minimum vertical load. It is important that such column strength not be degraded as the shape of the container changes as result of volumetric shrinkage within the container.
Moreover, a hot fill container must possess adequate hoop or circumferential strength in order to avoid excessive outward and inward bowing during changes of temperature and pressure, as well as to provide sufficient crush resistance when the container is gripped by a consumer.
There is significant price competition within the plastic packaging industry, and the cost of plastic resin is one of the main components of the price of hot fill containers. There is a fundamental tension between the strength requirements of such containers and the economic necessity to use as little plastic resin as possible in order to provide a functional container. In order to optimize column strength and hoop strength, a variety of different designs have been commercialized, using various features such as ribs and grooves that are defined within the sidewall of the container during the molding process.
One type of hot fill container that is disclosed in U.S. Pat. No. 7,604,140 to Pritchett et al. utilizes a plurality of vacuum panels that are arranged in a twisted or helical fashion about the periphery of the container. Such a helical vacuum panel configuration possesses certain advantages, because it provides inherent reinforcement in both the longitudinally and circumferential directions. In addition, such containers can be aesthetically pleasing to many consumers. However, such containers would be usable for more commercial packaging applications if they had improved crush resistance.
A need exists for an improved hot fill type container employing twisted or helical vacuum panels that exhibits superior crush resistance with respect to conventional containers of this type without requiring significant additional material.
Accordingly, it is an object of the invention to provide an improved hot fill type container employing twisted or helical vacuum panels that exhibits superior crush resistance with respect to conventional containers of this type without requiring significant additional material.
In order to achieve the above and other objects of the invention, a hot fill type plastic container according to a first aspect of the invention includes a finish portion that defines an opening and a main body portion having a sidewall that defines a plurality of vacuum panels and a plurality of creased wall portions. Each of the creased wall portions is positioned between two adjacent vacuum panels. At least one of the creased wall portions has an axis of longitudinal orientation when viewed in side elevation that has a vertical component and a circumferential component. The creased wall portions further preferably are substantially non-curved when viewed in side elevation.
A hot fill type plastic container according to a second aspect of the invention includes a finish portion that defines an opening and a main body portion having a sidewall that defines a plurality of vacuum panels and a plurality of creased wall portions. Each of the creased wall portions is positioned between two adjacent vacuum panels. At least one of the creased wall portions has an axis of longitudinal orientation when viewed in side elevation that has a vertical component and a circumferential component. The creased wall portions further preferably have a compound curvature to increase stiffness.
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 preferably includes a finish portion 12 having a rim 14 that defines an upper opening 16. A plurality of threads 18 may be defined on an outer surface of the finish portion 12 for securing a closure to the container 10.
Container 10 further includes a main body portion 20 having a sidewall 28 that defines an upper dome or shoulder portion 22 and a vacuum panel portion 24 that is constructed and arranged to deflect in response to internal volumetric changes during the hot fill process. Container 10 also includes a bottom portion 26 that is unitary with the vacuum panel portion 24, the dome portion 22 and the finish portion 12.
The vacuum panel portion 24 preferably includes a plurality of vacuum panels 30 and a corresponding plurality of creased wall portions 32 that are interposed between adjacent vacuum panels 30 about the periphery of the vacuum panel portion 24 of the main body portion 20. In other words, each of the creased wall portions 32 is preferably positioned between two adjacent vacuum panels 30. In the preferred embodiment, all of the creased wall portions 32 are preferably of substantially the same size and shape, and all of the vacuum panels 30 are also preferably substantially of the same size and shape.
At least one of the creased wall portions 32 preferably has an axis 33 of longitudinal orientation when viewed in elevation, as shown in
Each of the creased wall portions 32 is preferably oriented so that it is substantially parallel to an adjacent creased wall portion 32.
The main body portion 20 further preferably includes a first circumferential groove 34 that is proximate to an upper end of the respective vacuum panels 30. The first circumferential groove 34 preferably is substantially circular in transverse cross-section, and is oriented within a plane that is substantially perpendicular to the longitudinal axis 35 of the container 10.
An upper transition portion 38 is defined between the upper end of the respective vacuum panels 30 and the first circumferential groove 34. The upper transition portion 38 preferably includes a first portion 40 that is substantially circular in transverse cross-section. The upper transition portion 38 also preferably includes a plurality of second tapered portions 42 connecting the first portion 40 to the respective creased wall portions 32, and a plurality of third tapered portions 44 connecting the first portion 42 to the respective vacuum panels 30.
Referring to
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Preferably, a ratio R1/DMAX of the first average radius of curvature R1 to the maximum outer diameter DMAX of the container 10 is substantially within a range of about 0.01 to about 0.30, more preferably substantially within a range of about 0.03 to about 0.225 and most preferably substantially within a range of about 0.05 to about 0.150.
A ratio R2/DMAX of the second average radius of curvature R2 to the maximum outer diameter DMAX of the container 10 is preferably substantially within a range of about 0.01 to about 0.06, more preferably substantially within a range of about 0.02 to about 0.05, and most preferably substantially within a range of about 0.03 to about 0.04.
A ratio R2/R1 of the second average radius of curvature R2 to the first average radius of curvature R1 is preferably substantially within a range of about 0.27 to about 0.98, more preferably substantially within a range of about 0.35 to about 0.9 and most preferably substantially within a range of about 0.4 to about 0.8.
Referring to
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.
