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.
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 a 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.
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.
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 must 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 critical feature 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. 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.
In all the embodiments, 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.
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.