WO2007025251A2

WO2007025251A2 - Plastic container having a ring-shaped reinforcement and method of making same

Info

Publication number: WO2007025251A2
Application number: PCT/US2006/033517
Authority: WO
Inventors: Gregory Trude; Bret Sabold; Michael T. Kelly; Philippe Romuald
Original assignee: Graham Packaging Company, L.P.
Priority date: 2005-08-26
Filing date: 2006-08-28
Publication date: 2007-03-01
Also published as: WO2007025251A3; US20070045221A1

Abstract

A plastic container (10) comprises an upper portion (12) including a finish (18) adapted to receive a closure, a lower portion (14) including a base (22), a sidewall (16) extending between the upper portion and the lower portion, the sidewail having an interior surface and an exterior surface, and a substantially planar reinforcing ring (24) extending substantially perpendicularly from the interior surface of the sidewail. A method of making a plastic container, and a container preform, are also disclosed.

Description

PLASTIC CONTAINER HAVING A RING-SHAPED REINFORCEMENT AND

METHOD OF MAKING SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of co-pending United States Patent

Application No. 11/211,532, filed August 26, 2005, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

[0002] The present invention relates generally to plastic containers and methods of making plastic containers. More particularly, the present invention relates to plastic containers having a ring-shaped reinforcement and methods of making plastic containers having a ring- shaped reinforcement.

Related Ait

[0003] Plastic containers for storing contents such beverages, sauces, puddings, lotions, soaps, lubricants, and other objects are well known in the art. It is desirable for these plastic containers to have high hoop strength {i.e., the container's ability to resist ovalization and/or racking). In order to facilitate stacking and transportation, it is also desirable for plastic containers to have high top load capacity.

[0004] In order to increase the hoop strength of plastic containers, it is common for the container to have a recessed "waist" that extends around the circumference of the container, for example, near the vertical midpoint of the container, or just below the dome. However, containers having a conventional waist often exhibit greatly reduced top load capacity. In addition, the conventional waist often detracts from the visual appeal of the container, and/or limits the amount of designs that are possible for the container.

[0005] Therefore, there remains a need in the art for a plastic container having a reinforcement that provides increased hoop strength while maintaining top load capacity. There also remains a need in the art for such a plastic container that is visually appealing and provides a high degree of design flexibility. BRIEF SUMMARY OF THE INVENTION

[0006] The present invention is directed to a plastic container comprising an upper portion including a finish adapted to receive a closure, a lower portion including abase, a sidewall extending between the upper portion and the lower portion, the sidewall having an interior surface and an exterior surface, and a substantially planar reinforcing ring extending substantially perpendicularly from the interior surface of the sidewall.

[0007] According to one aspect of the invention, the sidewall includes an interior surface and an exterior surface, and the reinforcing ring extends from the interior surface. Additionally or alternatively, the exterior surface of the sidewall immediately opposite the reinforcing ring is substantially free of indentations. Additionally or alternatively, the exterior surface of the sidewall immediately opposite the reinforcing ring includes a seam.

[0008] According to another aspect of the invention, the reinforcing ring comprises a crease in the sidewall.

[0009] According to yet another aspect of the invention, the reinforcing ring comprises a first portion of the sidewall and a second portion of the sidewall that are folded over one another.

[00010] The reinforcing ring defines a nominal height and a nominal width, and the nominal width can be at least about three times the nominal height.

[00011] The present invention is also directed to a method of blow molding a plastic container, comprising inserting a preform into a mold, the preform comprising an upper portion, a lower portion, and a sidewall extending between the upper portion and the lower portion, stretching the preform with a stretch rod, contacting the stretch rod with a portion of the sidewall to form a ring of material around the stretch rod, and inflating the preform into a container. The ring of material forms a reinforcing ring on the container.

[00012] According to one aspect of the invention, the step of stretching the preform with the stretch rod causes the portion of the sidewall to contract around the stretch rod to form the ring of material. Additionally or alternatively, the method can further include the step of selectively forming a reduced-temperature region on the sidewall that substantially coincides with the portion of the sidewall that contracts around the stretch rod.

[00013] According to another aspect of the invention, the method can further include the step of preheating the preform to a first temperature. Additionally or alternatively, the method can include the step of cooling a portion of the sidewall to a second temperature less than the first temperature.

[00014] According to yet another aspect of the invention, the ring of material defines an upper section of the sidewall and a lower section of the sidewall, and during the step of inflating the preform into the container, a portion of the upper section and a portion of the lower section fold over one another.

[00015] The present invention is also directed a container preform, comprising an upper portion including a container finish, a lower portion including a closed end, and a sidewall extending between the upper portion and the lower portion, the sidewall comprising an angular transition area located between the container finish and the closed end.

[00016] According to one aspect of the invention, the sidewall further comprises a first wall portion located between the container finish and the angular transition area, the first wall portion defining a first wall thickness, and a second wall portion located between the closed end and the angular transition area, the second wall portion defining a second wall thickness, wherein the first wall thickness is different than the second wall thickness. For example, the first wall thickness can be less than the second wall thickness.

[00017] According to another aspect of the invention, the first wall portion can be substantially frusto-conical. According to yet another aspect of the invention, the second wall potion can substantially cylindrical. [00018] 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[00019] The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.

[00020] FIG. 1 is a perspective view of an exemplary embodiment of a plastic container according to the present invention; [00021] FIG. 2 is a side view of the plastic container of FIG. 1 ; [00022] FIG. 3 is a partial, cross-sectional view of an exemplary sidewall of the plastic container of FIG. 1; and

[00023] FIGS. 4 is a side view of one step in an exemplary embodiment of a method of blow molding a plastic container according to the present invention, with the mold shown in cross-section;

[00024] FIGS. 5-7 depict additional steps of the method of blow molding a plastic container, with the mold and a preform shown in cross-section; and

[00025] FIG. 8 is a side view of an exemplary embodiment of a container preform according to the present invention, with portions of the preform shown in cross-section.

DETAILED DESCRIPTION OF THE INVENTION

[00026] 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 departing from the spirit and scope of the invention. All references cited herein are incorporated by reference as if each had been individually incorporated.

[00027] Referring to FIGS. 1 and 2, an exemplary embodiment of a container 10 according to the present invention is shown. Container 10 can be used to package a wide variety of liquid, viscous, or solid products including, for example, juices or other beverages, yogurt, sauces, pudding, lotions, soaps in liquid or gel form, and bead shaped objects such as candy.

[00028] Container 10 generally includes an upper portion 12, a lower portion 14, and a sidewall 16 extending between upper portion 12 and lower portion 14. Upper portion 12 can include a finish 18 having one or more threads 20, or other features, configured to secure a closure, such as a cap (not shown) to container 10. Lower portion 14 can include a base 22 adapted to support container 10 in an upright position on a substantially flat surface, such as a table. Although not shown in the figures, base 22 can include any number of known features that reinforce the base 22, compensate for internal pressure or vacuum within container 10, or provide other desired functions. [00029] As shown in FIGS. 1 and 2, sidewall 16 is substantially tubular and has a generally circular transverse cross-section. However, one of ordinary skill in the art will appreciate that any cross-sectional geometry is possible. Other possible cross-sectional geometries include, for example, an oval transverse cross-section, a substantially square transverse cross-section, other substantially polygonal transverse cross-sectional geometries such as triangular or pentagonal, and combinations of curved and arced shapes with linear shapes. Irregular cross-sectional geometries are also possible. As will be understood, when container 10 has a substantially polygonal transverse cross-sectional geometry, the corners of the polygon are typically rounded or chamfered.

[00030] Still referring to FIGS. 1 and 2, container 10 includes a reinforcing ring 24 that extends from sidewall 16 around the circumference of container 10. As shown in the figures, reinforcing ring 24 may be substantially planar, and/or may be substantially perpendicular to sidewall 16. Reinforcing ring 24 can increase the hoop strength of sidewall 16 without significantly reducing the top load capacity of container 10. Reinforcing ring 24 is not limited to the position shown in FIGS. 1 and 2, and may be provided at any position along the height of container 10. In addition, container 10 may include any number of reinforcing rings 24 as may be needed to suit a specific application of container 10.

[00031] Referring to FIG. 3, sidewall 16 includes an interior surface 16A and an exterior surface 16B. In the embodiment shown, reinforcing ring 24 extends from interior surface 16A. The region of exterior surface 16B located immediately opposite reinforcing ring 24, indicated in FIG. 3 as R, is preferably substantially free of indentations. That is, region R preferably does not have an indentation corresponding in shape/size to reinforcing ring 24, as is typical of prior art containers. Rather, in the exemplary embodiment shown, region R includes at most only a minor seam 26, which only has minor effects on the aesthetics of container 10. The lack of any significant indentations in region R provides a container that has greater top load capacity when compared to conventional containers in which a reinforcing feature such as a ring or rib projecting from one side of the sidewall typically results in a corresponding indentation on the opposite side of the sidewall. hi addition, the lack of any significant indentation in region R provides a reinforcement that has minimal effect on the aesthetics of container 10, thus providing additional design flexibility.

[00032] Still referring to FIG. 3, reinforcing ring 24 may comprise a crease that is formed in sidewall 16, for example, during the process of making container 10. In the exemplary embodiment shown, reinforcing ring 24 comprises a first portion 24A and a second portion 24B. First portion 24A and second portion 24B can be pinched or folded over one another, for example, during blow molding of container 10, as will be described in more detail below.

[00033] As shown in FIG. 3, reinforcing ring 24 may define a nominal height Y that extends substantially parallel to the longitudinal axis of container 10, and a nominal width X that is perpendicular to the longitudinal axis. The nominal height Y and/or the nominal width X can be adjusted to provide certain characteristics to the container 10, such as hoop strength. According to one exemplary embodiment, nominal width X may be at least about three times the nominal height Y. [00034] Container 10 may be able to withstand the rigors of hot fill processing. In a hot fill process, a product is added to the container at an elevated temperature, about 82⁰C, which can be near the glass transition temperature of the plastic material, and the container is capped. As the container and its contents cool, the contents tend to contract and this volumetric change creates a partial vacuum within the container. In the absence of some means for accommodating these internal volumetric and barometric changes, containers tend to deform and/or collapse. For example, a round container can undergo ovalization, or tend to distort and become out of round. Containers of other shapes can become similarly distorted, hi addition to these changes that adversely affect the appearance of the container, distortion or deformation can cause the container to lean or become unstable. This is particularly true where deformation of the base region occurs. Container 10 withstands these tendencies by incorporating one or more reinforcing rings 24.

[00035] Container 10 can have a one-piece construction and can be prepared from a monolayer plastic material, such as a polyamide, for example, nylon; a polyolefin such as polyethylene, for example, low density polyethylene (LDPE) or high density polyethylene (HDPE), or polypropylene; a polyester, for example polyethylene terephthalate (PET), polyethylene naphtalate (PEN); or others, which can also include additives to vary the physical or chemical properties of the material. For example, some plastic resins can be modified to improve the oxygen permeability. Alternatively, the container can be prepared from a multilayer plastic material. The layers can be any plastic material, including virgin, recycled and reground material, and can include plastics or other materials with additives to improve physical properties of the container, hi addition to the above-mentioned materials, other materials often used in multilayer plastic containers include, for example, ethylvinyl alcohol (EVOH) and tie layers or binders to hold together materials that are subject to delamination when used in adjacent layers. A coating may be applied over the monolayer or multilayer material, for example to introduce oxygen barrier properties. In an exemplary embodiment, the present container is prepared from PET.

[00036] With reference to FIGS. 4-7, a method of blow molding a plastic container according to the present invention is shown and described. Prior to or concurrent with the blow molding process, a preform 40 is prepared from a thermoplastic material, for example, by an injection molding process. Referring to FIG. 4, one exemplary embodiment of preform 40 can include an open upper portion 42, a closed lower portion 44, and a sidewall 46 extending between the upper portion 42 and the lower portion 44. The upper portion 42 of preform 40 can include a finish having have one or more threads 48, or other features, formed thereon for securing a closure to the container once completed. Alternatively, the finish and/or threads can be formed during the blow molding process, as will be known by one of ordinary skill in the art. Preform 40 can generally define a longitudinal axis 49, shown in FIG. 4

[00037] Preform 40 is optionally preheated and then inserted into an open mold including mold halves 50A and 50B (shown in cross-section), which are closed about preform 40 and cooperate to provide a cavity 52 into which preform 40 is eventually blown to form a finished container. A stretch rod 54, shown in FIGS. 5-7, is then inserted into the open upper portion 42 of the preform 40 until it contacts the closed lower portion 44. Continued movement of stretch rod 54 in this direction (direction S in FIG. 5) stretches preform 40 along its longitudinal axis 49. Prior to or concurrent with this stretching operation, a small amount of air can optionally be "preblown" into preform 40 under low pressure through vents 56 in stretch rod 54 to partially inflate preform 40. [00038] As best shown in FIG. 5, stretching of the preform 40 along its axis 49 causes sidewall 46 to contract inward toward stretch rod 54. With sufficient stretching of preform 40 in this manner, sidewall 46 will contract until a portion of it contacts stretch rod 54, as shown, thereby forming a ring of material 58 extending around stretch rod 54. Due to possible temperature differences between the preform 40 (e.g., relatively warm) and the stretch rod 54 (e.g., relatively cool), the ring of material 58 may adhere to and/or harden around stretch rod 54. [00039] Preform 40 is next inflated under high pressure, for example, by blowing air through vents 56. As shown in FIG. 6, the regions of the sidewall 46 above and below the ring of material 58 initially expand outward due to the air pressure. The ring of material 58, however, remains adhered to and/or hardened around the stretch rod 54, and does not initially expand outward. The air pressure can cause the ring of material 58 to pinch away from sidewall 46, and can divide sidewall 46 into an upper section 46A and a lower section 46B, which may fold over on one another. Depending on the temperature of the preform 40, the upper section 46A and the lower section 46B may permanently bond to one another.

[00040] Continued application of high air pressure inside preform 40 eventually causes the ring of material 58 to expand away from stretch rod 54, and also causes the preform 40 to fully expand until it conforms to the mold cavity 52, as shown in FIG. 7. At this point, the container is fully formed, and the ring of material 58 forms a reinforcing ring that extends from the interior surface of the sidewall of the finished container. In the exemplary embodiment shown in FIG. 7, the reinforcing ring 58 is substantially planar and substantially perpendicular to the sidewall of the finished container.

[00041] At this point, the supply of air pressure can be turned off, and the stretch rod

54 can be removed. The mold halves 5OA and 5OB separate from one another and release the finished container.

[00042] In order to facilitate accurate placement of the reinforcing ring on the sidewall of the finished container, as well as consistent sizing of the reinforcing ring, it may be desirable to selectively form a reduced-temperature region on the portion of the preform 40 that coincides with the area of the finished sidewall where the reinforcing ring is to be located. This reduced- temperature region will have a higher strength as compared to the surrounding warmer areas, and will be more prone to contracting around the stretch rod 54 during the stretching process. The size and location of the reduced-temperature region can control the position and geometry of the resulting reinforcing ring on the finished container. The reduced-temperature region can be formed, for example, by preheating the preform 40 prior to placement in the mold, and subsequently cooling the desired region. Alternatively, the reduced-temperature region can be formed by heating the areas of the preform 40 surrounding the reduced-temperature region, but not the reduced-temperature region itself. One of ordinary skill in the art will appreciate that any number of other techniques can be implemented to create the reduced-temperature region. [00043] Referring to FIG. 8, an alternative embodiment of a preform according to the present invention is shown. Preform 140 can be used in the method described above in connection with FIGS. 4-7. Preform 140 can be configured to consistently and repeatedly locate the reinforcing ring (in the formed container) in the desired location. Preform 140 can include an open upper portion 142, a closed lower portion 144, and a sidewall 146 extending between the upper portion 142 and the lower portion 144. The upper portion 142 can include a container finish 147 having have one or more threads 148, or other features, formed thereon for securing a closure to the formed container. Preform 140 can generally define a longitudinal axis 149. [00044] The sidewall 146 can include an angular transition area 160 located, for example, between the container finish 147 and the closed end of the lower portion 144. The angular transition area 160 can divide the sidewall into two distinct regions, a first portion 146 A located between the container finish 147 and the angular transition area 160, and a second portion 146B located between the closed end of the lower portion 144 and the angular transition area 160. As shown in FIG. 8, the first portion 146A can be substantially frusto-conical in shape, although other configurations are possible. The second portion 146B can be substantially cylindrical in shape, although, again, other configurations are possible.

[00045] The first sidewall portion 146A can define a first nominal wall thickness 162.

The second sidewall portion 146B can likewise define a second nominal wall thickness 164. According to one exemplary embodiment, the first wall thickness 162 can be less than the second wall thickness 164, although other configurations are possible. For example, the first wall thickness 162 can alternatively be larger than the second wall thickness 164.

[00046] According to an alternative embodiment, not shown, the angular transition area 160 can be located in a different place than the transition from the first wall thickness 162 to the second wall thickness 164. For example, according to an exemplary embodiment, the angular transition area 160 can divide the sidewall into two portions both of substantially equal wall thickness. Additionally or alternatively, an increase or decrease in wall thickness can be located upstream or downstream of the transition area 160 {e.g., form a step in the sidewall).

[00047] The angular transition area 160, either alone or in combination with the difference between wall thicknesses 162, 164, can provide a targeted region of preform 140 that stretches more slowly than the surrounding areas. As a result, when preform 140 is stretched during the blow-molding process (e.g., with the stretch rod 54 shown in FIGS. 5-7 and described in connection therewith), the angular transition area 160 may be the first part of the preform 140 to contract inwards toward the stretch rod 54 and contact the stretch rod 54. Accordingly, the angular transition area 160 will typically form the ring of material around the stretch rod 54 that eventually becomes the reinforcing ring on the completed container. Therefore, by controlling the location, size, and other properties of the angular transition area 160, consistent and repeatable location, size, etc., of the reinforcing ring on the completed container can be achieved. The angular transition area 160 may be cooled during the blow molding process to further slow the stretching of this portion of the preform 140.

[00048] 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 present 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, within the scope of the claims and their equivalents, the invention may be practiced otherwise than as specifically described.

Claims

WHAT IS CLAIMED IS:

1. A plastic container comprising: an upper portion including a finish adapted to receive a closure; a lower portion including a base; a sidewall extending between the upper portion and the lower portion, the sidewall having an interior surface and an exterior surface; and a substantially planar reinforcing ring extending substantially perpendicularly from the interior surface of the sidewall.

2. The plastic container of claim 1 , wherein the exterior surface of the sidewall immediately opposite the reinforcing ring is substantially free of indentations.

3. The plastic container of claim 2, wherein the exterior surface of the sidewall immediately opposite the reinforcing ring includes a seam.

4. The plastic container of claim 1, wherein the reinforcing ring comprises a crease in the sidewall.

5. The plastic container of claim 1 , wherein the reinforcing ring comprises a first portion of the sidewall and a second portion of the sidewall that are folded over one another.

6. The plastic container of claim 1, wherein the reinforcing ring defines a nominal height and a nominal width, and the nominal width is at least about three times the nominal height.

7. A method of blow molding a plastic container, comprising: inserting a preform into a mold, the preform comprising an upper portion, a lower portion, and a sidewall extending between the upper portion and the lower portion; stretching the preform with a stretch rod; contacting the stretch rod with a portion of the sidewall to form a ring of material around the stretch rod; and inflating the preform into a container, wherein the ring of material forms a reinforcing ring on the container.

8. The method of claim 7, wherein the step of stretching the preform with the stretch rod causes the portion of the sidewall to contract around the stretch rod to form the ring of material.

9. The method of claim 8, further comprising the step of selectively forming a reduced-temperature region on the sidewall, wherein the reduced-temperature region substantially coincides with the portion of the sidewall that contracts around the stretch rod.

10. The method of claim 7, further comprising the step of preheating the preform to a first temperature.

11. The method of claim 10, further comprising the step of cooling a portion of the sidewall to a second temperature less than the first temperature.

12. The method of claim 7, wherein the ring of material defines an upper section of the sidewall and a lower section of the sidewall, and during the step of inflating the preform into the container, a portion of the upper section and a portion of the lower section fold over one another.

13. The method of claim 7, wherein the container includes a container sidewall having an interior surface and an exterior surface, and the reinforcing rings extends from the interior surface.

14. The reinforcing ring of claim 13, wherein the reinforcing ring is substantially planar and substantially perpendicular to the sidewall.

15. The method of claim 7, wherein the upper portion defines an opening in the preform, and the lower portion is closed, and the step of stretching the preform with the stretch rod includes inserting the stretch rod through the opening and contacting the closed lower portion.

16. The method of claim 7, wherein the upper portion comprises a container finish, the lower portion comprises a closed end, and the sidewall comprises an angular transition area located between the container finish and the closed end.

17. The method of claim 16, wherein the sidewall further comprises: a first wall portion located between the container finish and the angular transition area, the first wall portion defining a first wall thickness; and a second wall portion located between the closed end and the angular transition area, the second wall portion defining a second wall thickness; wherein the first wall thickness is different than the second wall thickness.

18. The method of claim 17, wherein the first wall thickness is less than the second wall thickness.

19. The method of claim 17, wherein the first wall portion is substantially frusto- conical.

20. The method of claim 19, wherein the second wall potion is substantially cylindrical.

21. The method of claim 16, wherein the angular transition area forms at least a part of the ring of material around the stretch rod.

22. A container preform, comprising: an upper portion including a container finish; a lower portion including a closed end; and a sidewall extending between the upper portion and the lower portion, the sidewall comprising an angular transition area located between the container finish and the closed end.

23. The container preform of claim 22, wherein the sidewall further comprises: a first wall portion located between the container finish and the angular transition area, the first wall portion defining a first wall thickness; and a second wall portion located between the closed end and the angular transition area, the second wall portion defining a second wall thickness; wherein the first wall thickness is different than the second wall thickness.

24. The container preform of claim 23, wherein the first wall thickness is less than the second wall thickness.

25. The container preform of claim 23, wherein the first wall portion is substantially fmsto-conical.

26. The container preform of claim 25, wherein the second wall potion is substantially cylindrical.