MXPA06002774A - Hot fill plasctic container with ressure absorption panels - Google Patents

Abstract

A plastic container is provided. The plastic container has a substantially cylindrical sidewall (110), a base (106) attached to a lower portion of the sidewall, a finish attached to an upper portion of the sidewall, and a vacuum panel (120) located in the sidewall. The container also has a raised island (130) protruding from the vacuum panel and surrounded by the vacuum panel, cross sectional areas of the island being defined as areas in horizontal planes of the container. The island has an upper portion (132), a middle portion (134) adjacent to the upper portion, and a lower portion (136) adjacent to the middle portion. A cross sectional area of the middle portion is less than a cross sectional area of the upper portion and less than a cross sectional area of the lower portion.

Description

PLASTIC CONTAINER FOR HOT FILLING, WITH PRESSURE ABSORPTION PANELS BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates generally to plastic containers and, more particularly, to hot-fill containers, which have vacuum panels resistant to deformation.

THE RELATED TECHNIQUE It is known to use blow molded plastic containers to pack "hot fill" beverages. In the process of filling a plastic container with a hot liquid, the pressure or vacuum imposed on the container can result in permanent deformation of the container. The side walls of the container can be deformed as the container is being filled with hot fluids. In addition, the rigidity of the container decreases after the hot filling liquid is introduced into the container. The temperatures used in these operations can be above the Tg of the plastic used (for example, PET), which can result in the deformation becoming permanent. Additionally, when the liquid is cooled, the gas that is also in the container decreases in volume, producing a vacuum in the container. Frequently hot-fill containers have substantially rectangular vacuum panels, which are designed to collapse inwardly when the container is cooled, after the hot-fill process. These vacuum panels help to reduce the undesirable deformation of the container by flexing inward, under vacuum pressure. When flexed inward, the vacuum panels relieve the pressure created by the vacuum and prevent or reduce the deformation of the other parts of the container. U.S. Patent No. 5,341,946 shows vacuum panels having multiple outwardly projecting portions, which are separated by a portion of the vacuum panel. U.S. Patent Nos. 5,279,433 and 6,016,932 show other configurations of the vacuum panels having projecting central portions. Yet another configuration of vacuum panels having projecting central portions is shown in WO 97/34808. The invention is directed to the design problems inherent with panel designs, discussed in the patents of the preceding references.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides an improved blow molded plastic container having an improved vacuum panel design. The design includes additional structural elements that resist the dilation tendencies present in the container structures of the prior art. The dilation results in the container bulging or taking the form of a barrel, due to the inherent pressure induced during the filling operation. The invention provides a panel having an enhanced island. The island may have a shape such that a portion of the island has a smaller cross-sectional area than the other portions of the island. For example, the island may have a smaller cross-sectional area in its central portion (in the vertical direction of the container). The smaller cross sectional area may be the result of the island having a horizontal rib, or the island having an "8" or peanut shaped configuration. In the case of a horizontal rib, the rib has a depth (in the radial direction of the container) such that the structure of the island is not completely divided by the rib. In other words, the rib is neither coplanar nor level with the surface of the vacuum panel. Preferably the rib has such a depth that there is sufficient island structure between the rib and the vacuum panel to prevent the rib from acting as a hinge between the divided portions of the island. The overall effect of the horizontal rib is to resist the expansion of the outer wall of the container. The bulge or "barrel shape" is prevented or decreased when the container is subjected to filling pressure at high temperatures. These structural improvements to resist the expansion can be used in conjunction with the panel technology that allows the increased flexing of the side walls of the vacuum panel, so that the pressure on the container can be easily accommodated. Reinforcing ribs of various types and in various locations can be used, as described above, to compensate for any excessive stress that will inevitably be present by the bending of the walls of the vessel to the new "pressure-adjusted" condition, by environmental forces . The island configured to the figure of "8" or peanut, works similar to the horizontal rib. The Ndentations associated with the configuration in Figure "8" or peanut, also impart a rigidity to the total structure of the side wall, to resist the bulging or barrel shape. The panel designs according to the invention, further, (1) improve the overall resistance to nicks due to the reduced vacuum pressure that is the result of the reduction in the volume of the product; (2) provide improved tag support; and (3) due to the reduced vacuum pressure, allow the reduction of container weights, which provides an increased number of design options for other container portions. Particular embodiments of the invention provide a plastic container having a substantially cylindrical side wall, a base attached to a lower portion of the side wall, an end cap secured to an upper portion of the side wall, and a vacuum panel, located on the side wall. An enhanced island protrudes from the vacuum panel and is surrounded by the vacuum panel; The cross sectional areas of the island are defined as areas in horizontal planes of the container. The island has an upper portion, a middle portion, adjacent to the upper portion, and a lower portion, adjacent to the middle portion. A cross-sectional area of the middle portion is smaller than a cross-sectional area of the upper portion, and smaller than a cross-sectional area of the lower portion. Other embodiments of the invention include adding two vertical ribs to the vacuum panel. The vertical ribs may be indentations on the vacuum panel. The island can be located between the vertical ribs. Other embodiments of the invention provide a method for reducing deformation in a plastic container. The method includes: providing the container with a substantially cylindrical side wall; providing in the container a base, fixed to a lower portion of the side wall; providing a top, fixed to an upper portion of the side wall, and providing a vacuum panel, located on the side wall. The method also includes providing an raised island protruding from the vacuum panel, and surrounded by the vacuum panel; the cross sectional areas of the island being defined as areas in the horizontal planes of the container. The island is provided with an upper portion, a middle portion, adjacent to the upper portion, and a lower portion, adjacent to the middle portion. A cross-sectional area of the middle portion is smaller than a cross-sectional area of the upper portion, and smaller than a cross-sectional area of the lower portion. Other objects and advantages, as well as the structure and function of the preferred embodiments, will become apparent from a consideration of the description, the drawings, the examples.

BRIEF DESCRIPTION OF THE DRAWINGS The above aspects and advantages, and others, of the invention will be apparent from the following, more detailed description of the preferred embodiments of the invention, which is illustrated in the accompanying drawings, in which the same reference numerals generally indicate identical, functionally similar and / or structurally similar elements. Figure 1 shows a vertical section of a container having vacuum panels known in the prior art. Figure 2 shows two horizontal sections of the middle panel of the container shown in Figure 1; one section shows the nominal cross section of the container, and the other shows the cross section of the container when under pressure. Figure 3 shows a side view of a container according to a first embodiment of the invention.

Figure 4 shows a vertical section of the container shown in Figure 3. Figure 5 shows two horizontal sections of the middle panel of the container shown in Figures 3 and 4; one section shows the nominal cross section of the container, and the other shows the cross section of the container when under pressure. Figure 6 shows a side view of a container according to a second embodiment of the invention. Figure 7 shows a vertical section of the container shown in Figure 6. Figure 8 shows two horizontal sections of the middle panel of the container shown in Figures 6 and 7; one section shows the nominal cross section of the container, and the other shows the cross section of the container when under pressure; and Figure 9 shows a side view of a container incorporating aspects of a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Some embodiments of the invention are discussed in detail below. In describing the modalities, specific terminology is used with clarity in mind. However, it is not intended that the invention be limited to the specific terminology thus selected. Even when specific example modalities are discussed, it should be understood that this is done for illustrative purposes only. Whoever has relevant experience in the art will recognize that other components and other configurations can be used without departing from the spirit and scope of the invention. All the references cited here are incorporated by means of your appointment, as if they had been incorporated individually. A thin-walled container, according to the invention, is intended to be filled with a liquid at a temperature above ambient temperature. According to the invention, a container of a plastic material can be formed, such as, for example, polyethylene terephthalate (PET) or polyester. One method for producing said container is by blow molding. The container can be filled by hot, automatic, high-speed filling equipment. Referring now to the drawings, Figure 1 shows a vertical section of a container 10 of the related art. The container 10 has a plurality of islands 20 located in the vacuum panels 30. Figure 2 shows two horizontal sections of the container 10. The section 12 shows the container 10 in a normal state, without tension. Section 14 shows a container 10 in a tensioned state, such as, for example, when the container 10 is filled with a hot liquid. It can be seen from Figure 2 that a substantial bulge, or a barrel shape, occurs when the container 10 is pressurized. The term "expanded circumferential length" will be used to describe the circumference of a horizontal section of the container 10 when it expands to its limit (a circle), as if subjected to a sufficient pressure to "straighten" all aspects of the cross section. The term "nominal circumference" will be used to describe the circumference of the smallest circle that completely encloses a particular cross section, when the container is in its normal state, without tension. The barrel shape seen in Figure 2 can be reduced by reducing the difference between the expanded circumferential length and the nominal circumference of at least one of the horizontal cross sections of a container. The reduction in the difference between the expanded circumferential length and the nominal circumference of a particular section decreases the barrel shape, because by doing so, the amount of dilation that is available before it reaches maximum dilation decreases. Figures 3 to 5 show a first embodiment of the invention. In this embodiment, the container 100 has a spout 102 for filling with fluid and supplying it; a bell 104, a base 106 and a body 110. The body 110 has a generally cylindrical shape and connects the base 106 with the bell 104. In this example, the body 110 has at least one area 112 for mounting a label, which it is located between (and includes) an upper label stop 114, and a lower label stop 116. One or more labels may be applied to area 112 for label assembly, using methods that are well known to those skilled in the art, including shrink wrap labeling methods and adhesive methods. The label may be extended around a portion of the label assembly area 112, or the entire area. Arranged within the mounting area of the label are a series of vacuum panels 120 which, in this example, are symmetrically distributed around the body 110. The vacuum panels 120 are flexed under the filling pressure and the subsequent cooling to adjust the pressure changes inside the container. An enhanced island 130 is located within at least one vacuum panel 120. In this example, each vacuum panel 120 surrounds an embossed island 130. The islands 130 help support the label and, in this example, are centrally located within the vacuum panels 120. Each island 130 has an average portion 134 and has an area of reduced cross section, as compared to an upper portion 132 and a lower portion 136. The cross-sectional areas are taken along horizontal planes of the container 100. The middle portion 134 in the example shown in Figures 3 to 5 is shaped of a horizontal rib 140. The horizontal rib 140 is parallel to the base 106, in this example; but alternatively it could not be parallel to the base 106. The size of the vacuum panels 120, the islands 130 and the horizontal ribs 140 may vary, depending on the size of the container, the composition of the plastic, the filling conditions of the bottle and the expected contents. Figure 5 shows a section taken along the line V-V of figure 3. Figure 5 shows the difference between the container 100, in a state without pressure (cross section 150) and a pressed state (cross section 152). By comparing Figure 5 with Figure 2 it can easily be seen that much less deformation is effected in the container 100 than in the container 10. It is also evident that the difference between the expanded circumferential length and the nominal circumference of the container 100 is smaller than that of container 10. This smaller difference is that which results in reduced deformation. The exact shape of the vacuum panels 120 is not critical to the invention. The vacuum panels 120 may be of any suitable type and may have various cross-sectional shapes. For example, vacuum panels 120 may be completely uniform or may have regions having various cross-sectional configurations, including flat, concave and convex shapes. The regions can be defined in terms of an upper area 122, an average area 124 and a lower area 126. The cross sectional shape of these individual areas can be selected and can be varied including flat, concave and convex shapes.

Figures 6 to 8 show a container 200 according to a second embodiment of the invention, in which the islands 230 are formed as a peanut, or as a figure of "8". Each island 230 has an average portion 234 having a reduced cross-sectional area, as compared to an upper portion 232 and a lower portion 236. The cross-sectional areas are taken along horizontal planes of the container 200. Contrary to the example shown in Figures 3 to 5 (where the cross-sectional area of the middle portion 234 is reduced by reducing its dimension in the radial direction), this embodiment reduces the cross-sectional area of the middle portion 234 by reducing its dimension in a circumferential direction . In other embodiments, the dimension of the middle portion 234 is also reduced in the radial direction. Figure 8 shows a section taken along the line Vlll-Vlll of figure 6, and shows the difference between the container 200 in normal state, without pressure (cross section 250) and in the state with pressure (cross section 252). By comparing Figure 8 with Figure 2, it can be easily seen that much less deformation occurs in the container 200 than in the container 10. It is also apparent that the difference between the expanded circumferential length and the nominal circumference of the container 200 is smaller than in container 10. This smaller difference is that which results in reduced deformation. Figure 9 shows a container 300 according to another embodiment of the invention which includes, in this example, two vertical ribs 360, located on the vacuum panels 320. In this example, the vertical ribs 360 are convex inwards, but could be alternately concave inward This configuration gives more flexibility to the vacuum panels 320, which can be advantageous in situations of high pressure, such as, for example, a flood with nitrogen. An example of particularly useful dimensions for vacuum panels and islands, is formed by the following: For the panel that has an island, with a horizontal rib, the panel has an approximate height of 8.83 cm and an approximate width of 4.79 cm . The rectangular island is placed centrally within the panel and has an approximate vertical length of 4.97 cm and an approximate width of 2.61 cm. The horizontal rib has an approximate depth of 4.44 mm when measured from the outermost surface of the island. The island has a thickness of approximately 6.07 mm when measured from its outermost surface to the inner surface of the panel. In some embodiments, the horizontal rib has a depth of at least half the thickness of the island. In other modalities the horizontal rib has a depth of at least two thirds of the thickness of the island. In other additional embodiments, the horizontal rib has a depth of at least three quarters of the thickness of the island. An example of particularly useful dimensions for the vacuum panel and the island in the form of peanuts, is as follows: The vacuum panel has the general dimensions indicated above. The island in the form of peanuts is centrally placed inside the panel and has the following dimensions. At its widest point, it has an approximate height of 24.75 mm and, at its narrowest point, it has an approximate width of 15.34 mm. The island has a thickness of approximately 6.07 mm when measured from its outermost surface to the inner surface of the vacuum panel. The above dimensions are offered only by way of example. The dimensions are a function of the size of the container and can be increased or decreased, depending on the size and functional requirements of the container. It should be understood that even when numerous features and advantages of the present invention have been pointed out in the preceding description, along with details of the structure and function of the invention, the description is only illustrative, and changes can be made in the details, especially in matters such as the configuration, size and disposition of the parties, within the principles of the invention. All references cited in this description are incorporated herein by reference. The discussion of the references here is simply intended to summarize the assertions made by their authors, and it is not admitted that any reference constitutes prior art relevant to patentability.

Applicants reserve the right to challenge the accuracy of the references cited. The modalities illustrated and discussed in this specification are intended only to teach those having experience in the field, the best way known to the inventors to make and use the invention. Nothing in this description should be considered as limiting the scope of the invention. All the examples presented are representative and not restrictive. The embodiments of the invention described hereinabove may be modified or may be varied, without departing from the invention, as will be appreciated by those having experience in the art, in light of the foregoing teachings. Accordingly, it should be understood that the invention may be practiced in another manner than is specifically described herein.

Claims (18)

1. - A plastic container, characterized in that it comprises: a substantially cylindrical side wall; a base fixed to a lower portion of the side wall; a top fixed to an upper portion of the side wall; an enhanced island, which protrudes from the vacuum panel, and is surrounded by the vacuum panel; the cross-sectional areas of the island being defined as areas in horizontal planes of the container; an upper portion of the island; a middle portion of the island adjacent to the upper portion; and a lower portion of the island adjacent to the middle portion; where a cross-sectional area of the middle portion is smaller than a cross-sectional area of the upper portion, and smaller than the cross-sectional area of the lower portion.

2. The container according to claim 1, further characterized in that the island has the shape of a peanut.

3. The container according to claim 1, further characterized in that the middle portion is a substantially horizontal rib having a depth in the radial direction of the container that is less than the depth, in the radial direction, of one of the upper portion. and the lower portion.

4. The container according to claim 3, further characterized in that the depth of the middle portion is less than half the depth of one of the upper portion and the lower portion.

5. The container according to claim 4, further characterized in that the depth of the middle portion is less than one third of the depth of one of the upper portion and the lower portion.

6. The container according to claim 5, further characterized in that the depth of the middle portion is less than a quarter of the depth of one of the upper portion and the lower portion.

7. The container according to claim 1, further characterized in that the raised island is bisected by the middle portion.

8. The container according to claim 1, further characterized in that it additionally comprises a plurality of vacuum panels spaced symmetrically around the side wall.

9. The container according to claim 8, further characterized in that each of the vacuum panels has an raised island that projects from it and is surrounded by it; the cross-sectional areas of the island being defined as areas in horizontal planes of the container; having each island: a higher portion; a middle portion, adjacent to the upper portion; and a lower portion adjacent to the middle portion; where a cross-sectional area of the middle portion is smaller than a cross-sectional area of the upper portion, and smaller than a cross-sectional area of the lower portion.

10. The container according to claim 1, further characterized in that the vacuum panel has two vertical ribs.

11. The container according to claim 10, further characterized in that the vertical ribs are indentations in the vacuum panel.

12. The container according to claim 11, further characterized in that the island is located between the vertical ribs.

13. A method for reducing deformation in a plastic container, characterized in that said method comprises: providing in the container a substantially cylindrical side wall; providing in the container a base, fixed to a lower portion of the side wall; providing a fastener attached to an upper portion of the side wall; provide a vacuum panel located on the side wall; provide an enhanced island that protrudes from the vacuum panel and is surrounded by the vacuum panel; the cross-sectional areas of the island being defined as areas in horizontal planes of the container; provide a superior portion of the island; provide a middle portion of the island, adjacent to the upper portion; and provide a lower portion of the island, adjacent to the middle portion; where a cross-sectional area of the middle portion is smaller than a cross-sectional area of the upper portion and smaller than a cross-sectional area of the lower portion.

14. The method according to claim 13, further characterized in that the island provided has the shape of a peanut.

15. The method according to claim 13, further characterized in that the middle portion is provided as a substantially horizontal rib having a depth, in a radial direction of the container, that is less than the depth, in the radial direction, of a between the upper portion and the lower portion.

16. The method according to claim 15, further characterized in that the depth of the middle portion is less than half the depth of one of the upper portion and the lower portion.

17. The method according to claim 13, further characterized in that the raised island is bisected by the middle portion.

18. The method according to claim 13, further characterized in that it further comprises providing a plurality of vacuum panels, spaced symmetrically around the side wall; where each of the vacuum panels is provided with an enhanced island that protrudes from and is surrounded by it; the sectional areas of the island being defined as areas in horizontal planes of the container; having each island: a higher portion; a middle portion, adjacent to the upper portion; and a lower portion, adjacent to the middle portion; where a cross-sectional area of the middle portion is smaller than the cross-sectional area of the upper portion, and smaller than the cross-sectional area of the lower portion. 10. The method according to claim 13, further characterized in that the vacuum panel is provided with two vertical ribs; the vertical ribs being indentations in the vacuum panel; and the island is located between the vertical ribs.