Method and Apparatus for Inerting Head Space of a Capped Container

Abstract

A process to reduce oxygen in the head space of non-pressurized containers comprises injecting an inert gas into the container head space and into the cap during the capping process. In an alternative embodiment, inert gas is injected into the caps at one or more points along the conveyance rout to the capping point.

Description

RELATED APPLICATION

This application is a continuation-in-part application claiming the benefit of pending U.S. patent application Ser. No. 11/029,326 filed Jan. 5, 2005, entitled Method and Apparatus for Inerting Head Space of a Capped Container.

TECHNICAL FIELD OF THE INVENTION

This invention relates to bottling of potable fluids subject to microbial attack. In particular, the invention relates to a method and apparatus for extending the shelf life of such potable fluids stored in non-pressurized containers with snap-on caps by at least partially displacing the oxygen in the cap and in the container head space with an inert gas.

BACKGROUND OF THE INVENTION

It has long been recognized that removing gaseous oxygen from sealed containers containing potable liquids can extend their shelf lives by reducing the rate of spoiling from microbial attack. Vacuum packaging and the use of bags have been used to eliminate gas altogether from packaging, but inerting, or the filling of the unfilled container space with an inert gas, is also widely used.

In a popular method of inerting, a small dose of liquid nitrogen is injected into a filled container just prior to capping. The nitrogen vaporizes, which displaces oxygen from the container's head space during capping. Some liquid nitrogen remains in the container after capping and vaporizes in the sealed container, which pressurizes the container. However, this method is not useful for non-pressurized containers such as milk and juice bottles. The snap-on caps for these containers are not designed to withstand the pressures developed by the vaporized nitrogen, and the increased pressure created by the vaporized nitrogen breaks the seal between the cap and bottle, allowing air to be sucked back into the container during handling and shipping, renewing microbial attack. As a result, shelf life of non-pressurized capped containers is not significantly extended using this method.

Methods have been developed for inerting the head space in non-pressurized containers such as the classic gable-top paper container. U.S. Pat. No. 6,634,157 issued to Anderson et al. on Oct. 21, 2003 discloses an apparatus and method for filling these containers. It makes used of a special nozzle inserted into the container after filling with product and prior to sealing the container. The inerting step must be carried out as a separate step between filling and sealing the container, and therefore adds more time to the overall packaging cycle, which reduces throughput. Also, the apparatus for positioning, operating and removing the nozzle is complex and relatively expensive.

A need remains for an inexpensive method and apparatus for inerting a non-pressurized beverage container. Such a method preferably should work with established capping apparatuses and require a minimum of space for the inerting apparatus. In addition, a method and apparatus that can perform the inerting without adding additional time to the overall filling/sealing procedure would be considered advantageous.

SUMMARY OF THE INVENTION

In general, an invention having the desired features and advantages is achieved by injecting an inert gas such as nitrogen simultaneously into the head space of a filled container and the cap used to seal the container during the capping procedure. Preferably, the apparatus for injecting the apparatus includes at least one injector oriented downward at an angle between about fifteen and forty degrees from horizontal, and preferably between about twenty and twenty-five degrees, and aimed into the top of the container neck just at or before the point at which the cap initially contacts the container. The velocity of nitrogen flow should be low enough to prevent splashing of container contents, and preferably is low enough to avoid visibly disturbing the fluid surface. However, in every case the flow rate must be enough to reduce the oxygen level in the sealed container to an amount below about fourteen percent oxygen by volume, and preferably below about twelve percent by volume. While nitrogen is preferred for economic reasons, other inert gases known in the art can also be used.

An alternate embodiment of the apparatus employs separate injectors, one directed into the container and another into the cap at or near the point where the cap engages the container. In yet another embodiment, inert gas is injected into the cap at more than one point along the cap's conveyance route immediately prior to engaging and sealing the container. The flow rates for the different injection streams can be equivalent or differ substantially from each other.

The present invention has advantages over other methods and apparatus for inerting. Less equipment and space is needed than for apparatus using an inert gas filled environment. The apparatus for carrying out the method of the invention can easily be adapted to existing capping equipment. The inerting process can be carried out between filling and capping the container without adding any time to the overall process. Additional features and advantages of the invention will become apparent in the following detailed description and in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front schematic elevation of a preferred apparatus used to practice the process of the invention;

FIG. 2 is a right side elevation of the apparatus shown in FIG. 1;

FIG. 3 is a front elevation for an alternate apparatus embodiment; and

FIG. 4 is a front elevation for another apparatus embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 show a typical apparatus for capping one-gallon plastic milk bottles. The apparatus 11 is shown in schematic with nonessential equipment removed for visibility. Throughout the figures, which are not drawn to scale, equivalent elements are given identical reference numbers. While snap-on caps are shown, it is believed screw-on caps can also make use of the method of the invention for low pressure service, i.e., service in which the pressure in the sealed head space can range from slightly below to slightly above atmospheric pressure when capped, but not at high enough pressure to require a container with features designed to handle elevated pressure (e.g. bottles for carbonated beverages). Therefore, the term ‘cap having a top member and a skirt depending from the top member and defining a skirt volume’ is intended to include both the snap-on caps shown and screw-on caps.

A chute 13 is used to transport caps 15 to the bottles 17. Each cap 15 has a top member 19 and a skirt 21 depending from the top member 19 and defining a partially enclosed skirt volume 23 with the top member 19. At the end of the chute 13, a pivotable arm (not shown) holds the next cap 15 to be used in the proper position for being put onto a bottle 17. As the bottle 17 moves along the conveyer track 25 past the cap 15, the skirt 21 engages the bottle 17. The moving bottle biases the cap 15 so that it is released by the pivotable arm and passes under a plate 29 that biases the cap downward, sealing it onto the bottle 17.

The apparatus 11 of the invention comprises a pair of injectors 31, 33 made from nominal half-inch copper tubing mounted on a header block 35 which in turn is attached by an adjustable linkage 37 to the chute 13. Flexible tubing 39 connects the header block 35 to a supply of pressurized nitrogen, preferably through a control loop having a control valve and flow controller (not shown), although other schemes can be used such as manually operated throttling valve and a pressure gauge located between the valve and the header block 35. An alternative embodiment is envisioned but not shown, wherein the header block 35 is absent and the injectors 31 and 33 are individually supplied by flexible tubing or other suitable conduit to the pressurized inert gas supply.

Because the injectors may be located close to the chute 13, the injectors 31 and 33 are separated by a gap 41 to allow tags 43 extending from the caps 15 to pass between the injectors unobstructed. While simple copper tubing is shown, other types of injectors known in the art can also be used, including other cross sectional types such as dispersion fans. Jets and devices that produce a narrow gas stream are not prohibited but are not preferred since a narrow, high velocity gas stream is more likely to produce splashing or otherwise disturb the surface of the container contents. Regardless of the injector shape, a feature of at least one embodiment is the proper orientation of the injectors 31, 33 so that the inert gas stream is directed at or just below the point where the cap skirt 21 initially engages the bottle, in order to ensure that both the bottle head space and the cap skirt volume are properly flushed by the inert gas. The adjustable linkage 37 allows the user to experiment with orientation for best results with various equipment models, when the apparatus 11 is retrofit on existing capping equipment. However, the adjustable linkage can be replaced with a fixed mounting bracket or other unadjustable hardware for a particular piece or model of equipment or when manufactured as an integral part of the capping equipment.

The flow of nitrogen is set from about fifty to about two hundred standard cubic feet an hour (SCFH) to ensure the desired reduction of the oxygen level in the head space of a one-gallon milk container. The injectors operate continuously, so that there is some waste of the inert gas in the time interval between containers. The injectors are angled at about fifteen to forty degrees from horizontal, and preferably from about twenty to twenty-five degrees from vertical, and oriented so that a significant part of the flow stream flushes the skirt volume 23. As mentioned above, these angles are preferable in order to be able to flush both the head space and cap skirt volume, particularly at a time when the cap and container are brought into a close relationship. Preferably, the flow direction of the inert gas is directed toward a point at which the cap and container come into contact. In at least one embodiment, wherein the cap and container are initially engaged, the opening of the container may define a horizontal plane and the opening of the cap skirt volume may define a plane which is angularly offset from the plane defined by the container opening. In this way, with the appropriate nozzle angles and inert gas flow direction, the flushing of the cap skirt volume and head space may be optimized. This is necessary because trials have shown that the gas trapped in the skirt volume 23 tends to displace gas from the head space during capping rather than being pushed out into the surrounding environment, so that the gas composition in the cap has a significant impact on the final gas composition in the sealed head space.

FIG. 3 shows an apparatus for use with another embodiment of the invention. This embodiment differs from the preferred embodiment in that the inert gas is injected separately into the head space and the skirt volume by two independent injectors 45 and 47. While this apparatus also works well, it is more sensitive to proper construction and orientation for optimal performance. Therefore, this embodiment is better suited to a fixed installation as shown, rather then being adjustable, although adjustability can still be used. FIG. 4 extends the use of multiple injectors even farther. In this embodiment, the inert gas is injected into the caps at more than one point along the delivery chute. The flow rates of the various injection streams can be set equal to each other, or varied as desired. Also, in the embodiments of FIGS. 3 and 4 it is possible, although not shown, to use different inert gases for the different injectors. For example, argon may be preferred for use in flushing the head space, as argon is significantly denser than air and will form a fairly stable and distinct layer within the head space, so that filling the head space will effectively prevent oxygen in the air from settling back into the head space. While carbon dioxide will also work well from a technical standpoint, it is not preferred as it tends to affect the taste of the container contents. Argon's density and tendency to stratify, which help when inerting the head space, work against it in attempting to effectively inert the skirt volume, which is inverted. Here, nitrogen may be more desirable, as it more nearly matches the density of air, and does not stratify, so that it will tend to remain in the skirt volume longer.

In at least one embodiment, the flow of inert gas is selected so that the oxygen level in the sealed container is less than about fourteen percent by volume, and preferably less than about twelve percent by volume. By contrast, the prior art does not mention any allowable upper limit for oxygen content, and generally implies that proper inerting requires removal of essentially all oxygen from the head space. The inventor has discovered that practical extension of shelf life occurs even when oxygen levels in the head space are as high as about fourteen percent, with shelf life increasing with decreasing oxygen level. As the oxygen level is reduced below six percent by volume, there is a diminishing returns to how much shelf life is extended with reduced oxygen level. The discovery that the head space need not be flushed completely free of oxygen makes the present methods and apparatus practical. For example, it is not necessary to insert an inert gas injector into the head space in order to ensure complete flushing of the head space, so the apparatus can be achieved without interfering with the conventional operation of the capping equipment, so there is no throughput penalty. Since complete removal of oxygen is not required, there is no need to create an oxygen-free environment around the container during capping, which eliminates the need for expensive, complicated and bulky apparatus for creating an artificial contained atmosphere around the bottles.

Preferably, the inert gas supply comprises ambient inert gas which is delivered to the cap skirt volume and head space at a relatively low pressure of below ten pounds per square inch (psi), and at a relatively low flow rate of below eight cubit feet per minute (cfm). This allows the inert gas to displace the oxygen in the head space of the filled and sealed container. These and other parameters discussed herein (such as nozzle angles, for example) contribute certain benefits to the inerting process. For instance, the inerting process may be accomplished without any, or without excessive, splashing of the contents of the container. Also, the inert gas may fill the cap skirt volume and container head space without drawing in excessive amounts of oxygen from the surrounding environment. This helps in achieving gas compositions in the sealed head space of less than about fourteen percent (14%) oxygen. More preferably, the gas composition is less than about five percent (5%) oxygen. By carefully controlling the flow pressure, rate, volume, and direction, gas compositions of less than about three percent (3%) oxygen may be achieved.

The invention has several advantages over the prior art. The method can be carried out simultaneously and independently of the conventional capping process, so throughput is essentially unchanged. The apparatus is simple and inexpensive to install, and requires relatively little space, especially in comparison to methods and apparatus that create an enclosed low-oxygen atmosphere surrounding the containers during capping. Existing capping equipment can be easily retrofitted to practice the method of the invention.

The invention has been shown in several embodiments. It should be apparent to those skilled in the art that the invention is not limited to these embodiments, but is capable of being varied and modified without departing from the scope of the invention.

Claims

1. A method for extending shelf life of a potable liquid in a container sealed by a cap having a top member and a skirt depending from the top member and defining a skirt volume, the container defining a head space above the potable liquid, comprising the step of:

bringing the container and the cap into a close relationship;

injecting an inert gas into the container head space and the skirt volume; and

sealing the cap on the container with a gas composition in the head space comprising less than about fourteen percent oxygen by volume.

2. The method of claim 1, wherein the gas composition comprises less than about five percent (5%) oxygen.

3. The method of claim 1, wherein the gas composition comprises less than about three percent (3%) oxygen.

4. The method of claim 1, wherein the cap initially contacts the container in an inclined orientation during the sealing step, and the inert gas is injected at or near the point where the cap and the container initially come into contact during the sealing step.

5. The method of claim 1, wherein the gas composition in the sealed head space is less than about twelve percent oxygen by volume.

6. The method of claim 1, wherein the inert gas is injected by at least one injector, and the at least one injector simultaneously injects inert gas into both the container head space and the cap skirt volume.

7. The method of claim 1, wherein the inert gas is injected by at least a first injector and a second injector, the first injector injecting inert gas into the container head space and the second injector injecting inert gas into the cap skirt volume.

8. The method of claim 7, wherein the same inert gas is injected by the first injector and the second injector.

9. The method of claim 7, including a first inert gas and a second inert gas, the first and second inert gases being different, wherein the first injector injects the first inert gas and the second injector injects the second inert gas.

10. The method of claim 1, further comprising the step of injecting an inert gas into the cap skirt volume prior to the step of bringing the container and the cap into a close relationship.

11. The method of claim 7, wherein a gas composition in the sealed head space is less than about twelve percent oxygen by volume.

12. The method of claim 10, wherein a gas composition in the sealed head space is less than about twelve percent oxygen by volume.

13. An apparatus for inerting the head space of a capped container, comprising:

a pressurized supply of an inert gas; and

at least one injector connected to the pressurized supply of the inert gas, the at least one injector operable to simultaneously inject the inert gas into a head space of a container and into a skirt volume of a cap used to seal the container such that the inert gas is directed at or below a point where the cap initially engages the container.

14. The apparatus of claim 13, the nozzle being adjustable from a first position in which gas is directed toward at least the head space at a first angle and a second position in which gas is directed toward at least the head space at a second angle.

15. The apparatus of claim 13, further comprising a header block connected between the pressurized supply of the inert gas and the at least one injector.

16. The apparatus of claim 13, wherein the at least one injector is angled from about fifteen to about forty degrees from horizontal.

17. The apparatus of claim 13, wherein the at least one injector is angled from about twenty to about twenty-five degrees from vertical.

18. The apparatus of claim 13, wherein the inert gas is nitrogen.

19. An apparatus for inerting the head space of a capped container, comprising:

a pressurized supply of an inert gas;

at least one first injector connected to the pressurized supply of the inert gas, the at least one first injector angled from about fifteen to about forty degrees from horizontal and operable to inject the inert gas into a head space of a container; and

at least one second injector connected to the pressurized supply of the inert gas, the at least one second injector operable to inject the inert gas into a skirt volume of a cap used to seal the container.

20. The apparatus of claim 19, further comprising a header block connected between the pressurized supply of the inert gas and the at least one first injector.

21. The apparatus of claim 19, further comprising a header block connected between the pressurized supply of the inert gas and the at least one second injector.

22. The apparatus of claim 19, wherein the at least one first injector is angled from about twenty to about twenty-five degrees from vertical.

23. The apparatus of claim 19, wherein the at least one second injector is angled from about fifteen to about forty degrees from horizontal.

24. The apparatus of claim 19, wherein the at least one second injector is angled from about twenty to about twenty-five degrees from vertical.

25. The apparatus of claim 19, wherein the inert gas is nitrogen.

26. An apparatus for inerting the head space of a capped container, comprising:

a pressurized supply of a first inert gas;

a pressurized supply of a second inert gas different than the first inert gas;

at least one first injector connected to the pressurized supply of the first inert gas, the at least one first injector operable to inject the first inert gas into a head space of a container; and

at least one second injector connected to the pressurized supply of the second inert gas, the at least one second injector operable to inject the second inert gas into a skirt volume of a cap used to seal the container.

27. The apparatus of claim 26, further comprising:

a first header block connected between the pressurized supply of the first inert gas and the at least one first injector; and

a second header block connected between the pressurized supply of the second inert gas and the at least one second injector.

28. The apparatus of claim 26, wherein the at least one first injector is angled from about fifteen to about forty degrees from horizontal.

29. The apparatus of claim 26, wherein the at least one first injector is angled from about twenty to about twenty-five degrees from vertical.

30. The apparatus of claim 26, wherein the at least one second injector is angled from about fifteen to about forty degrees from horizontal.

31. The apparatus of claim 26, wherein the at least one second injector is angled from about twenty to about twenty-five degrees from vertical.

32. The apparatus of claim 26, wherein the first inert gas and second inert gas are nitrogen.

33. An apparatus for inerting the head space of a container, comprising:

an insert gas source;

at least one nozzle coupled to the inert gas source, the at least one nozzle operable to create a gas flow having a direction, the gas flow being directed toward a cap used to seal the container when the cap is angled relative to an opening of the container, so that the gas flow simultaneously impinges a skirt volume of the cap and a head space of the container.

34. An apparatus for inerting the head space of a container, wherein a cap is used to seal the head space, the cap being conveyed along a first route and the container being conveyed along a second route, the cap and the container being conveyed toward one another to be brought into contact, the apparatus comprising:

an inert gas source;

at least one nozzle coupled to the inert gas source, the at least one nozzle operable to direct an inert gas to at least one of a skirt volume of the cap and the head space of the container at least two distinct points during conveyance of the respective cap and container.

35. The apparatus of claim 34, wherein the nozzle is operable to direct the inert gas toward the container head space at first and second distinct points during conveyance of the container.

36. The apparatus of claim 34, wherein the nozzle is operable to direct the inert gas toward the cap skirt volume at first and second distinct points during conveyance of the cap.

37. The apparatus of claim 34, wherein the nozzle is operable to direct the inert gas toward the container head space at a first point during conveyance of the container and toward at least the cap skirt volume at a second point during conveyance of the container.

38. The apparatus of claim 37, wherein the nozzle is operable to direct inert gas toward the cap skirt volume at a first point during conveyance of the container and toward at least the cap skirt volume at a second point during conveyance of the container.

39. An apparatus for inerting the head space of a container, comprising:

an inert gas source;

at least one nozzle coupled to the inert gas source and operable to direct an inert gas to at least one of the head space and a skirt volume of a cap used to seal the container, the nozzle further operable to produce an inert gas flow at a pressure of less than about 10 psi.

40. An apparatus for inerting the head space of a container, comprising:

an inert gas source;

at least one nozzle coupled to the inert gas source and operable to direct an inert gas to at least one of the head space and a skirt volume of a cap used to seal the container, the nozzle further operable to produce an inert gas flow at a flow rate of less than about 8 cfm.

41. An apparatus for inerting the head space of a container, comprising:

an inert gas source;

at least one nozzle coupled to the inert gas source and operable to direct an inert gas to at least one of the head space and a skirt volume of a cap used to seal the container, the nozzle further operable to produce an inert gas flow at a pressure and flow rate to avoid drawing external oxygen into the head space to inert the head space to a gas composition level of less than about fourteen percent (14%) oxygen when the container is capped.

42. The apparatus of claim 41, wherein the gas composition is less than about twelve percent (12%) oxygen.

43. The apparatus of claim 41, wherein the gas composition is less than about five percent (5%) oxygen.

44. The apparatus of claim 41, wherein the gas composition is less than about three percent (3%) oxygen.