Patent Application
20060175284
1. Field of the Invention
The present invention relates generally to plastic containers, and more particularly to hot-fillable containers.
2. Related Art
The use of blow molded plastic containers for packaging liquid product in “hot fill” applications is known. The term “hot fill” can be considered any temperature higher than room temperature. However, when referring to “hot fill” applications, conventional temperatures used in such applications are at least 180° F.
In the process of filling a plastic container with hot fill product, pressure or vacuum imposed on the container can result in permanent deformation of the container. The sidewalls of the container can deform as the container is being filled with hot fluids. In addition, the rigidity of the container decreases after the hot fill liquid is introduced into the container. The temperatures employed in these operations may be above the transition temperature (Tg) of the plastic used (for example PET), which can result in the deformation becoming permanent. In addition, as the liquid cools in a sealed container, gas that is also in the container shrinks in volume, producing a pressure less than atmospheric (or a “vacuum”) in the container.
Hot fill containers often have substantially rectangular vacuum panels that are designed to collapse inwardly as the contents of the container cool after the hot-fill process. These vacuum panels help reduce unwanted deformation of the container by flexing inward under the pressure of the vacuum. By flexing inward, the vacuum panels relieve the pressure created by the vacuum and prevent or reduce the deformation of other parts of the container.
U.S. Pat. No. 5,341,946 discloses vacuum panels having multiple outwardly projecting portions which are separated by a portion of the vacuum panel. U.S. Pat. Nos. 5,279,433 and 6,016,932 disclose other configurations of vacuum panels having projecting center portions. Yet another configuration of vacuum panels having projecting center portions is disclosed in WO 97/34808.
A particularly persistent problem in the manufacture of plastic containers is known in the industry as “lightweighting.” Typically, lightweighting involves redesigning a package to use less plastic material, which also tends to make the container weigh less. Manufacturers continue to develop new technologies that enable them to reduce the amount of PET resin needed to make a bottle without compromising performance. These efforts are extremely important to reduce manufacturing costs because PET resin accounts for a significant portion of the cost of the finished container. However, lightweighting of a container can result in thinner container walls. As a result, such lightweighted containers are more subject to deformation. Thus, there is a continuing need for containers that are lightweighted but still resist deformation.
The present invention provides an improved blow molded plastic container. More particularly, the present invention provides an improved blow molded PET container suitable for accommodating a hot-fill product.
The plastic container in accordance with one embodiment of the present invention includes a heel portion having an enclosed base; a body portion transitioning into the heel portion, the body portion being defined at least in part by a plurality of generally flat panels forming a generally tubular structure, with each of the panels being connected to an adjacent panel with a chamfered post and with the body portion including at least one vertically oriented rib at each of the chamfered posts; a bell portion transitioning into the body portion; and a finish attached to the bell portion and defining an opening.
In another embodiment of the invention, the bell portion may be circular in cross-section and the body portion is one of triangular or rectangular in cross-section, The transition between the bell portion and the body portion would accommodate the circular cross-section of the bell portion to the approximately triangular or rectangular or square cross-section of the body portion.
The transition between the bell portion and the body portion generally includes an upper bumper, and the transition between the body portion and the heel portion generally includes a lower bumper.
The body portion generally includes a vertically oriented rib on either side of each of the chamfered posts. The vertically oriented ribs resist expansion of the outer walls of the container. The vertical ribs further provide an improved top loading capability.
Generally, the upper bumper may be defined by discontinuous, substantially horizontal ribs, and the lower bumper may be defined by discontinuous, substantially, horizontal ribs. In an exemplary embodiment, the upper bumper may be defined by four discontinuous horizontal ribs, and the lower bumper may be defined by four discontinuous horizontal ribs.
In an alternate embodiment, the upper bumper may be defined by at least one ring extending around the plastic container, and the lower bumper may be defined by at least one ring extending around the plastic container.
In a yet another exemplary embodiment, the base is a push-up base.
In a still further exemplary embodiment, at least one of the plurality of panels may be a vacuum panel.
The plastic container according to an exemplary embodiment may have a body portion with a cross-sectional diameter, which is about 86% to about 95% of the cross-sectional diameter of one of the heel and bell portions. For example, in an 8 ounce container, the cross-section of the body portion is about 86% of the cross-section of the bell portion or the heel portion. Other larger and smaller embodiments, of the same or different proportions, can also be provided.
In an exemplary embodiment, the body portion, the heel portion, and the bell portion are adapted for hot-fill applications and are blow molded PET.
The present invention also provides a method of reducing deformation in a plastic container, which includes: providing a heel portion having an enclosed base; providing a body portion transitioning into the heel portion, the body portion being defined at least in part by a plurality of generally flat panels forming a tubular structure, with each of the panels being connected to an adjacent panel with a chamfered post and with the body portion having at least one vertically oriented rib at each of the chamfered posts; providing a bell portion transitioning into the body portion; and providing a finish attached to the bell portion and defining an opening. At least one of the plurality of panels can include a vacuum panel.
The present invention further provides a method of manufacturing a blow molded PET container from a preform, which includes disposing a preform in a mold cavity having an interior surface, the cavity interior surface having a heel portion region defining an enclosed base; a body portion region transitioning into the heel portion region, the body portion region being defined at least in part by four generally flat panels and generally square shaped in cross-section, wherein each of the panels is connected to an adjacent panel with a chamfered post and wherein the body portion region includes at least one vertically oriented rib at each of the chamfered posts; a bell portion region transitioning into the body portion region; and defining an opening. The preform is then distended against said mold surface to form the container.
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.
The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.
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. 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. All references cited herein are incorporated by reference as if each had been individually incorporated.
A thin-walled container in accordance with the invention is intended to be filled with a product at a temperature above room temperature. Typically, the product is at about 180° F. According to the invention, a container may be formed from a plastic material such as, for example, polyethylene terephthlate (PET) or polyester. One method of producing such a container is blow molding. The container can be filled by automated, high speed, hot-fill equipment.
Referring now to the drawings,
As shown particularly in
The body portion 108 may have one or more generally flat panels 116 disposed within the label mounting area 114 to form a generally tubular structure. In the exemplary embodiment illustrated in
According to the invention, the tubular structure of body portion 108 may be formed so that adjacent panels of the body section form an approximate angle in the range of about 60° to about 90°. For example, if three generally flat panels are used the angle formed between adjacent panels would be approximately 60° and the generally tubular structure would have an approximately triangular shape. A body section 108 having four generally flat panels would have an angle of approximately 90° between adjacent panels. At least one of the generally flat panels 116 can be a vacuum panel for accommodating interior and exterior pressure changes. For example, vacuum panels flex under the pressure of hot filling and subsequent cooling to adjust for pressure changes within container. Standard vacuum panel, and/or high efficiency vacuum panel technology can be incorporated into the generally flat panels 116. In an exemplary embodiment of the present invention, at least two of the generally flat panels 116 are vacuum panels. An exemplary high efficiency vacuum panel is disclosed in International Application No. PCT/NZ00/00019, published as Publication No. WO 00/50309.
Panel designs in accordance with the invention (1) improve overall dent resistance due to reduced vacuum pressure resulting from product volume reduction, (2) provide improved label support, and (3) because of reduced vacuum pressure, allow the reduction of container weights, affording an increased number of design options for other container portions. Vacuum panels can be of any appropriate type and can have various cross-sectional shapes. For example, vacuum panels can be entirely uniform or have regions having various cross-sectional shapes including flat, concave and convex.
The body portion 108 may transition into the heel portion 106 and the bell portion 104 with an extended curved feature. Generally, the extended curved feature may be the joining of a generally circular shape to a generally square shape by a smooth outwardly curved changing radius that is tangential to each feature. While the embodiment shown in
The ratio of the body portion 108 to the heel portion 106 and the bell portion 104 can be defined for a single serve container. Generally, conventional single serve packages have a height ratio of body portion to the bell and heel portions of about 1:1. In the exemplary embodiment, the height ratio of the body portion 108 to the bell or heel portions 104, 106 is about 2.3:1. In another exemplary embodiment, the height ratio of the body portion to the heel portion may be approximately 3.3:1; and the height ratio of the body portion to the bell portion may be about 1.6:1. Thus, depending upon the volume of the container, the height ratio of the bell or heel portion to body portion may vary from 1.6-3.3:1.
The body portion 108 further includes at least one vertically oriented rib 120. In exemplary embodiments, two vertical ribs 120 are arranged at each chamfered corner and bound the generally flat panels 116. That is, a vertical rib 120 may be disposed on either side of a post 118 thereby forming a chamfered corner. The vertical ribs may be formed by grooves or flutes. The grooves or flutes of the chamfered corner may be beveled or rounded. In the embodiment shown in
As shown in the embodiments of
The overall effect of the horizontal ribs is to resist the expansion of the outer wall of the container. Bulging or “barreling” is prevented or diminished when the container is subjected to fill pressure at high temperatures. These structural improvements to resist expansion can be used in conjunction with panel technology that allows for increased flexing of the vacuum panel sidewalls so that the pressure on the container may be more readily accommodated. Reinforcing ribs of various types and location may still be used, as described above, to compensate for any excess stress that will inevitably be present from the flexing of the container walls into the new “pressure-adjusted” condition by ambient forces.
In addition, the vertical ribs 120 are similar to the horizontal ribs 122 in that the vertical ribs 120 aid in reducing and/or preventing deformation. In particular, the vertical ribs 120 aid in reducing and/or preventing the effect that the generally flat panels 116 have on deforming the chamfered corners when under pressure.
The size of the generally flat panels 116, the horizontal ribs 122, 124, and the vertical ribs 120 may vary depending on container size, plastic composition, bottle filling conditions and expected contents.
In the exemplary embodiment shown in
An example of particularly useful dimensions for the container of the present invention follows: the body portion 108 has a cross-sectional diameter of about 1.890 inches and the heel portion 106 and bell portion 104 each have a cross-sectional diameter of about 2.205 inches. The cross-sectional diameter of the body portion may be about 84-95% of the cross-sectional diameter of the bell or heel portion. The finish 102 may have a diameter of about 1.390 inches. The container 100 may have a height of in the range of 5.0-5.8 inches. Smaller heights are possible if the cross-sectional diameters of the container increase. Likewise, smaller or larger heights are possible depending upon the amount of volume in a container and the diameter of the container.
The above dimensions are offered by way of example only. The dimensions are a function of the size of the container and may be increased or decreased depending on the size and performance requirements of the container. The increased or decreased dimensions can be proportionate to the exemplary dimensions or disproportionate to the exemplary dimensions.
In an alternative embodiment, as shown in
Furthermore, combinations of horizontal ribs and continuous rings can be utilized to achieve the desired characteristics. The rings 128, 130 provide additional stability as compared to the horizontal ribs 122, 124 shown in the embodiment of
The container can be made of plastics such as polyesters, for example polyethylene terephthalate (PET); polyolefins, for example polyethylene and polypropylene; and polyamides, such as nylons. The structures can by formed of a single layer or multiple layers of like or different materials. The side walls can include additives, for example materials to improve barrier properties, or to bind various layers.
All references cited in this specification are hereby incorporated by reference. The discussion of the references herein is intended merely to summarize the assertions made by their authors and no admission is made that any reference constitutes prior art relevant to patentability. Applicants reserve the right to challenge the accuracy and pertinence of the cited references.
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 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. It is therefore to be understood that the invention may be practiced otherwise than as specifically described.
