NITROGEN DOSED BASE

Abstract

A container base that is capable of withstanding an internal pressure and further capable of causing an even deflection, such as that created by introducing liquefied gas during a hot filling process. The base includes a heel with a standing ring disposed at a lower portion thereon. A generally concave push up portion extends radially inward from the standing ring portion. At least two reinforcing rings are disposed on the push up portion, wherein the reinforcing rings diminish uneven deflection to prevent the container from tipping while resting on a flat surface.

Description

FIELD OF THE INVENTION

The present invention relates to plastic containers, and more particularly to plastic containers capable of receiving positive internal pressure.

BACKGROUND OF THE INVENTION

Plastic containers have been replacing metal and glass containers with increasing frequency due to the many advantages that plastic provides. The safety and appeal of plastic containers have been enhanced further by the development of hot filling processes, in which a product is introduced into the container at an elevated temperature and then immediately sealed. By hot filling, such products are adequately sterilized.

When a beverage or product is hot filled, however, the beverage temperature imposes mechanical stresses on the container's structure. For example, as the hot-filled liquid cools, it decreases in volume which has the effect of producing a negative pressure in the container. As a result, the hot filled containers deform, affecting their aesthetics. Accordingly, hot filling capabilities have spurred the development of related technologies to address problems of container deformation.

One approach to counteract negative internal pressure from a hot filling application is employing vacuum panels or other structures that flex or deform. Multiple designs and approaches to vacuum panels in the container sidewalls have been developed. For example, some designs provide ribs to increase hoop stiffness and eliminate bulges while integral vacuum panels collapse inwardly.

Furthermore, bases for hot filled containers have been developed that are capable of withstanding internal negative pressures. Typically, the bases contain a continuous standing ring and a ribbed recess portion. In order to promote flexing or deformation, the standing rings are usually quite large and substantially flat in order to accommodate the internal negative pressure. The ribs of the container bases generally are configured to control only inwardly directed forces and deformation.

Another approach to prevent deformation is called nitrogen dosing. Liquid nitrogen will expand to its gas form when released into the atmosphere. The actual volume of the gas is many times greater than the volume in its liquid state. Therefore, if a small amount of liquid nitrogen is placed in the headspace of a container just before the capping point, the liquid will still be expanding once the lid is sealed. As the liquid changes to gas, its volume will increase, which to some extent counteracts the negative pressure induced by the decrease of the hot filled contents upon cooling. U.S. Pat. No. 5,251,424 (Zenger), generally describes nitrogen dosing for hot fill bottles, but such a method has not been widely commercialized.

It is a goal of the present invention to provide a base, and corresponding container, that is capable of withstanding positive internal pressure and reducing deflection as a result of nitrogen dosing.

SUMMARY OF THE INVENTION

A base is provided for a container that is suitable for withstanding internal pressurization and reducing deflection as a result of nitrogen dosing. The bottle may be used for hot filling or filling at ambient temperatures. The base includes a heel, a standing ring, a push up portion, and a plurality of ribs. The heel is curved in transverse cross section. The standing ring is located at the lower portion of the heel and includes circumferentially spaced apart contact portions that are generally arcuate in transverse cross. The push-up portion generally is concave and extends radially inward from the standing ring portion. The push-up portion includes a gate area, a first circular reinforcing ring and a second circular reinforcing ring. Finally, a plurality of ribs extend radially outwardly from the gate portion, through the first and second reinforcing rings and through the standing ring.

The base geometry preferably does not contain any flat area, to reduce the deflection as a result of nitrogen dosing. The base geometry is designed to sag down, but not touch the standing surface. The reinforcing ribs incorporated at the base, contain and diminish uneven deflection so that the bottle doesn't tilt to one side. Accordingly, a base capable of withstanding internal positive pressure and diminishing uneven deflection as a result of nitrogen dosing is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an embodiment of a container illustrating aspects of the present invention;

FIG. 2 is a bottom view of the container shown in FIG. 1;

FIG. 3 is a cross sectional view of the container shown in FIG. 1; and

FIG. 4 is a cross sectional view of a portion of the rib taken through line 4-4 of FIG. 2.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

A container 10 is capable of withstanding internal positive pressure. In a preferred embodiment container 10 generally includes a neck 12, a body 16, and a base 20. Neck 12 extends downward into body 16 and base 20 extends downward from a lower portion of body 16. Neck 12 generally is a rigid ring adapted to receive and withstand the mechanical loads imposed by a threaded closure (Not shown). Body 16 can be formed into a myriad of configurations to provide the desired structural characteristics, aesthetic qualities, and product identification. Generally, neck 12 and body 16 may be of any design.

Base 20 generally includes a heel 24, a standing ring 26, a push-up portion 28 and a plural ribs 30. Heel 24 generally is curved in transverse cross section and extends downwardly from body 16 merging smoothly into standing ring 26. Preferably there are no flat surfaces in the standing ring area. Standing ring 26 may include circumferentially spaced apart contact portions 34. Contact portions 34 are generally arcuate in transverse cross. Container 10, generally rests on contact portions 34 while in an upright position.

Push-up portion 28 is generally concave and extends radially inward from standing ring 26. Push-up portion 28 contains a gate area 40, a first reinforcing ring 43, and a second reinforcing ring 47. Gate area 40 preferably is disposed at the center of push-up portion 28. Gate area 40 preferably includes a recess 60 located substantially at the center of gate 40 for receiving a preform's gate during blow molding. Gate area 40 may also include a depression 62 formed by pinning a portion of gate area 40 between the distal ends of a stretch rod and a mold. Second reinforcing ring 47 is substantially circular and disposed proximate standing ring 26. First reinforcing ring 43 is also substantially circular and disposed between gate area 40 and second reinforcing ring 47. Preferably, reinforcing rings 43 and 47 are generally concave, however, they are not limited to such a design.

Ribs 30 generally extend radially outward from gate area 40, through first reinforcing ring 43, through second reinforcing ring 47, and through standing ring 26. Ribs 30 preferably are concave and contain a trough 52 over at least a portion of its radial length, wherein trough 52 preferably has an upper rib surface 56. Preferably, upper surface 56 is substantially flat, however, is not limited to such a design. Preferably, base 20 has six ribs 30 and six contact portions 34, however, the design is not limited to such a configuration and may change depending on the size of the container.

Container 10 having base 20 as described herein is intended to be filled at an elevated temperature, and base 20 is configured to receive contents at up to approximately 212 degrees F. without failure, although such temperature is not a limit to the scope of the invention. In this regard, a plastic resin preferably having an intrinsic viscosity of over approximately 0.75 may be employed, more preferably over approximately 0.80, and most preferably approximately 0.84 may be employed. The present invention is not limited to such viscosities, which are provided only for guidance.

Upon introduction of the contents into container 10, a predetermined quantity of liquefied gas is introduced therein. The liquefied gas, which preferably is liquefied nitrogen, quickly vaporizes. After capping, the vaporization increases the internal pressure within container 10. Preferably, the internal pressure range is 15 to 35 psi at hot-fill temperature, and 0-10 psi upon cooling to ambient temperature (approximately 72 degrees). The pressure ranges are provided to be exemplary, and the scope of the present invention is not limited to such pressure ranges.

Techniques for introducing liquefied gas into container 10 are well known, especially by persons familiar with such technology for introducing liquefied nitrogen into metal cans. Such nitrogen dosing systems are commercially available and nearly exhaustively described in the literature. The present invention is not limited to a particular means for introducing liquefied gas, but rather encompasses any introduction technology. The magnitude of the dose of liquefied gas introduced into the container may be determined according to such parameters as contents temperature, headspace volume, characteristics of the container (including its elasticity or relationship between volume change and pressure), order of introduction of the product and nitrogen dose (that is, whether the nitrogen dose is introducing into the container before, concurrently with, or after the contents), and the time period between introducing the nitrogen dose and capping or sealing. Choosing the magnitude of the dose of liquefied gas for a particular application will be straightforward for persons familiar with liquefied gas dosing technology, such as, for example, as used in the metal can industry, in light of the present disclosure and the above parameters.

The internal positive pressure within container 10 acts on all surfaces of base 20. Thus, pressure urges push-up portion 28 substantially downwardly, urges against the interior surfaces of ribs 30 substantially downwardly and substantially inwardly, urges against the interior surface of standing ring 26 substantially downwardly, urges against the interior of heel 24 substantially outwardly and somewhat downwardly, and in particular urges against the interior surface of the area between reinforcing rings 43 and 47 substantially downwardly. Each of the downward components of the pressure vectors, as well as most of the other components of the pressure vectors, urges base 20 toward inversion. The term “substantially downwardly” as used herein refers generally to the downward direction when the container is upright, and may also include a lateral component.

Conventional bases often fail under such conditions either by complete inversion, which is a complete failure mode in which much of push-up portion 28 is pushed fully out the bottom of base 20 to break the plane defined by standing ring 26, or by partial inversion, in which a portion of standing ring 26 (most often a single circumferential location) is pushed downwardly relative to the plane defined by the as-molded standing ring. Even a partial inversion of small magnitude might destroy or inhibit the container's ability to solidly rest on a flat surface.

To withstand this positive internal pressure, a draft surface connected to the standing ring has been utilized. The draft surface deforms substantially downwardly in response to the internal pressurization of the container. The container is then still able to rest on the standing ring even after the internal pressurization. Unfortunately, the deformed draft surfaces can deform unevenly thereby causing the bottle to tilt.

In the present embodiment standing ring 26 is stiffened by ribs 30, thereby diminishing downward deflection of standing ring 26, upon pressurization of base 20, compared with an unstiffened configuration. Reinforcing rings 43 and 47 contain and cause an even deflection in substantially a downward direction, thereby preventing the bottle from tilting once pressurized. Also, the base geometry preferably does not contain any flat area, to help reduce such deflection. Thus, standing ring 26, ribs 30, and reinforcing rings 43 and 47 each enhance the stability of container 10 when standing upright on standing ring 26 and help contain and cause an even deflection.

Preferably, base 20 in its fully deformed or deflected state, does not interfere with standing ring 26 such that standing ring 26 remains circumferentially continuous. In this regard the deflected surfaces do not extend downwardly below standing ring 26 even in its deformed or deflected state such that substantially all of standing ring 26 is substantially planar.

Persons familiar with preform and blow molding processes and technology in light of the present disclosure will be enabled to configure a container that employs the present invention(s). Preferably, to enhance the ability of the bottle to remain vertical without listing under internal pressure, the gate is pinned to the center and does not deviate. Furthermore, it is preferable that the material is evenly distributed around the base to obtain the full benefits of the invention. Accordingly, pinning the gate at the center and providing an even material distribution, results in an even height increase and the bottle will not tilt while under pressure.

Container 10 may be formed of conventional plastics suitable for cold filling, such as commonly used for water or like, non-carbonated beverages. Container 10 may also be formed of conventional thermoplastic suitable for conventional hot-filling. Persons familiar with container engineering in light of the present disclosure will be able to engineer a container by choosing parameters (such as polymer choice, intrinsic viscosity, blow molding or other forming techniques, and the like) so as to practice each aspect of the invention disclosed herein.

The present invention is illustrated in the particular embodiment described above. The invention, however, is not limited to this embodiment, but rather encompasses structure and the related function as defined in the claims. For example, the structure of the bottle has advantages for use with positive internal pressure, but the present invention is intended to be limited to positive internal pressure applications unless expressly recited in the claims.

Claims

1. A plastic bottle suitable for containing a non-carbonized beverage, said bottle comprising:

a body and a neck that terminates in a finish;

an enclosed based extending from a lower portion of the body, said base comprising: a heel that is curved in transverse cross section; a standing ring portion disposed at a lower portion of the heel, the standing ring portion includes circumferentially spaced apart contact portions, each one of the contact portions being generally arcuate in transverse cross, the bottle resting on the contact portion while upright; a generally concave push-up portion extending radially inwardly from the standing ring portion, the push-up portion including: (i) a gate area substantially at a center thereof, (ii) a first substantially circular reinforcing ring disposed proximate the standing ring portion, and (iii) a second substantially circular reinforcing ring disposed between the gate area and the first reinforcing ring; and plural ribs extending radially outwardly from the gate portion, through the first and second reinforcing rings, and through the standing ring,

whereby the reinforcing rings contain deflection and diminish uneven deflection of the base in response to positive internal pressure.

2. The bottle of claim 1 wherein the base resists inversion by uniformly transmitting forces to the contact portion of the standing ring.

3. The bottle of claim 1 wherein the first reinforcing ring and the second reinforcing ring are generally concave.

4. The bottle of claim 1 wherein the gate area includes a recess in the center thereof for receiving a preform's gate during blow molding.

5. The bottle of claim 1 wherein the gate area includes a depression formed by pinning a portion of the gate area between a distal end of a stretch rod and a mold.

6. The bottle of claim 1 wherein the rib has a substantially flat trough over at least a portion of its radial length.

7. The bottle of claim 6 wherein the trough is substantially flat over most of the radial length of the rib.

8. The bottle of claim 1 wherein each surface of the standing ring is arcuate in transverse cross section.

9. The bottle of claim 1 wherein each surface of the push-up portion is arcuate in transverse cross section.

10. The bottle of claim 1 wherein the quantity of contact portions is at least six and the quantity of ribs is at least six.

11. A method of filling a plastic container comprising the steps of:

(a) providing a container that includes: a body and a neck that terminates in a finish; an enclosed based extending from a lower portion of the body, said base comprising: a heel that is curved in transverse cross section; a standing ring portion disposed at a lower portion of the heel, the standing ring portion includes circumferentially spaced apart contact portions, each one of the contact portions being generally arcuate in transverse cross, the bottle resting on the contact portion while upright; a generally concave push-up portion extending radially inwardly from the standing ring portion, the push-up portion including: (i) a gate area substantially at a center thereof, (ii) a first substantially circular reinforcing ring disposed proximate the standing ring portion, and (iii) a second substantially circular reinforcing ring disposed between the gate area and the first reinforcing ring; and plural ribs extending radially outwardly from the gate portion, through the first and second reinforcing rings, and through the standing ring;

(b) introducing a liquid into the container;

(c) introducing a liquefied gas into the container; and

(d) capping or sealing the container after the introducing steps (b) and (c);

whereby the reinforcing rings contain deflection and diminish uneven deflection of the base in response to positive internal pressure.

12. The method of claim 11 wherein the step of introducing the liquid includes introducing the liquid at an elevated temperature.

13. The method of claim 11 wherein the step of introducing the liquid includes introducing the liquid approximately at ambient temperature.

14. The method of claim 11 wherein the base resists inversion by uniformly transmitting forces to the contact portion of the standing ring.

15. The method of claim 11 wherein the gate area includes a recess in the center thereof for receiving a preform's gate during blow molding.

16. The method of claim 11 wherein the gate area includes a depression formed by pinning a portion of the gate area between a distal end of a stretch rod and a mold.

17. The method of claim 11 wherein the rib has a substantially flat trough over at least a portion of its radial length.

18. The method of claim 17 wherein the trough is substantially flat over most of the radial length of the rib.

19. The method of claim 11 wherein each surface of the standing ring is arcuate in transverse cross section.

20. The method of claim 11 wherein each surface of the push-up portion is arcuate in transverse cross section.