Patent Application
20200130248
This invention relates generally to the field of blow molded plastic containers, and specifically to a hot fill type container having a dome portion that is shaped to provide superior crush resistance.
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. However, some hot fill type containers are designed without vacuum panels, and are engineered to assume vacuum uptake through inward deflection of features of the container, such as the dome portion.
The dome portion of a blow molded plastic container forms the shoulder of the container and is typically positioned between an upper finish portion that defines an opening and is designed to receive a closure. The dome portion of certain types of predecessor hot fill containers was prone to denting as a result of physical contact and vacuum forces within the container. While it is possible to strengthen the dome portion by engineering it to have a thicker sidewall, this is problematic in the sense that it requires more material to make the container, which adds to the expense of the container.
A need therefore exists for a hot fill container having a dome configuration that provides superior crush resistance with respect to predecessor containers without significantly increasing material costs.
Accordingly, it is an object of the invention to provide a hot fill container having a dome configuration that provides superior crush resistance with respect to predecessor containers without significantly increasing material costs.
In order to achieve the above and other objects of the invention, a plastic container according to one aspect of the invention includes a finish portion that defines an opening, a bottom portion and a substantially cylindrical main body portion having a first maximum diameter. The container further includes a dome portion having a first curved portion and a second curved portion that has a different curvature than the first curved portion. The dome portion also defines a second maximum diameter that is greater than the first maximum diameter.
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
Hot fill plastic container 10 is preferably fabricated from a material such as polyethylene terephthalate (PET) using a conventional stretch reheat blow molding process. Alternatively, plastic container 10 could be fabricated using an extrusion blow molding technique, from a material such as polyethylene, polypropylene or polyolefin.
Plastic container 10 includes a bottom portion 16, which is preferably shaped so as to be substantially cylindrical and to define a standing ring that permits the container 10 to be stably supported by an underlying horizontal surface. Container 10 further includes a substantially cylindrical main body portion 18, which in the preferred embodiment includes a plurality of cylindrical sidewall portions 20 that are separated by a corresponding plurality of stiffening grooves 22. The main body portion 18 has a first maximum outer diameter D1, as is shown in
Plastic container 10 further includes a dome portion 24 positioned between the main body portion 18 and the finish portion 12. Dome portion 24 defines a second maximum diameter D2, which is preferably greater than the first maximum diameter D1 of the main body portion 18. The cylindrical sidewall of the bottom portion 16 defines a third maximum outer diameter D3, which preferably is greater than the maximum outer diameter D1 of the main body portion 18 and substantially the same as the maximum outer diameter D2 of the dome portion 24.
The dome portion 24 preferably has a convex outer surface 26 that is shaped so as to define a first convex portion 28 that has a first average radius of curvature R1. In the preferred embodiment, the first average radius of curvature R1 is substantially constant. The convex outer surface 26 further includes a second convex portion 30 having a second average radius of curvature R2, which in the preferred embodiment is also substantially constant. A transition region 32 connects the first and second convex portions 28, 30.
The dome portion 24 preferably has an egg-shaped appearance, as may be seen in
In this embodiment, the transition region 32 is preferably located near the portion of the convex outer surface 26 that defines the maximum outer diameter D2. The compound curve shape created by the first and second convex portions 28, 30 creates a stiffening effect at the transition region 32 that provides enhanced crush resistance at the point that the dome portion 24 is expected to make contact with adjacent containers or to be gripped by a consumer.
The second radius of curvature R2 of the second convex portion 30 is preferably greater than the first radius of curvature R1 of the first convex portion 28. A ratio R1/R2 of the first radius of curvature R1 to the second radius of curvature R2 is preferably substantially within a range of about 0.3 to about 0.9, more preferably substantially within a range of about 0.4 to about 0.8 and most preferably substantially within a range of about 0.5 to about 0.7.
A ratio R1/D2 of the first radius of curvature R1 to the maximum diameter D2 of the dome portion is preferably substantially within a range of about 0.4 to about 1.2, more preferably substantially within a range of about 0.55 to about 1.05 and most preferably substantially within a range of about 0.7 to about 0.9.
A ratio of the first maximum outer diameter D1 of the main body portion 18 to the second maximum outer diameter D2 of the dome portion 24 is preferably substantially within a range of about 0.8 to about 0.99, more preferably substantially within a range of about 0.85 to about 0.98 and most preferably substantially within a range of about 0.9 to about 0.97.
As
A hot fill plastic container 40 that is constructed according to a second, preferred embodiment of the invention is depicted in
Container 40 further includes a dome portion 42 defining a convex outer surface having a first convex portion 50 having an average radius of curvature R3, which in the preferred embodiment is substantially constant. Dome portion 42 further defines a second convex portion 52 having an average radius of curvature R4, which is also preferably substantially constant. A transition region 54 connects the first and second convex portions 50, 52. In this embodiment, the maximum outer diameter of the dome portion 42 is positioned below the transition region 54 and defined by the second convex portion 52.
As was described above with respect to the first embodiment, the dome portion 42 defines a maximum outer diameter D2 that is preferably greater than the maximum outer diameter D1 of the main body portion 18 and preferably substantially the same as the maximum outer diameter D3 of the bottom portion 16.
Dome portion 42 advantageously has a circumferential groove 48 defined near a lowermost end thereof. The circumferential groove 48 provides additional stiffening to the dome portion 42, which enhances its crush resistance. The circumferential groove 40 preferably extends around the entire circumference of the lower part of the dome portion 42. Circumferential groove 40 further preferably has an average concave radius of curvature R5 and a maximum depth DG.
Preferably, a ratio DG/D2 of the depth DG of the groove 48 to the maximum outer diameter D2 of the dome portion 42 is substantially within a range of about 0.01 to about 0.15, more preferably substantially within a range of about 0.02 to about 0.10 and most preferably substantially within a range of about 0.03 to about 0.09.
A ratio R5/DG of the average concave radius of curvature R5 of the groove 40 to the depth DG of the groove 48 is preferably substantially within a range of about 0.2 to about 1.0, more preferably substantially within a range of about 0.35 to about 0.9 and most preferably substantially within a range of about 0.5 to about 0.8.
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.
