PRESSURE SEALING METHOD FOR HEADSPACE MODIFICATION
A container cap (80) positioned within a sealing chamber (84) has an openable aperture to allow the increase in pressure in the container headspace (231) before the aperture is resealed. In alternative embodiments the container (1) may include vacuum compensation panels (801, 802,803, 804) in its sidewall and/or base.
This invention relates generally to a method of light-weighting containers by modifying the pressure in the headspace and a container utilising that method. The pressure modification may be undertaken either during the sealing of the container, or after sealing the container. This headspace modification may be achieved by filling a container with a liquid, sealing the contents of the container from contamination from outside air, and adjusting the pressure of the headspace either during the capping process or after the container has been capped or sealed. The headspace modification process increases the volume of content within the container, thereby increasing the internal pressure within the container. This action in turn may displace the liquid below the headspace in the upper neck region of the container downwardly prior to or after capping of the container, providing for increased top-load capability for the container. This invention may further relate to hot-filled and pasteurized products packaged in heat-set polyester containers.
BACKGROUNDMost production facilities are searching for ways to reduce costs as a small savings on the cost of each single container, for a food or beverage packer, this quickly adds up to tremendous savings, based on the large number of containers processed. Utilizing lighter weight containers or reducing utility costs are good savings methods.
However, lighter weight containers for noncarbonated products can collapse when stacked unless special handling requirements are satisfied. One typical method used to increase stacked weight capability, or top-load strength, in cold fill containers is to dose the container with liquid nitrogen prior to capping. When dosed into a container, liquid nitrogen will provide some internal pressure, which allows the containers to be stacked several pallets high. Gaseous nitrogen is one utility used in the food and beverage industry to expel oxygen from products and increase shelf life.
However, as the nitrogen disperses immediately upon injection the process for controlling accurate dosing is limited. Some of the nitrogen will escape prior to capping, thus rendering the process inexact in terms of absolute pressurisation control. Additionally, handling nitrogen systems can be costly and dangerous.
Nitrogen consumption can be reduced by as much as 80% using a liquid nitrogen dosing system instead of gaseous nitrogen tunnels, but as the capping or sealing of the container occurs at ambient pressure at the precise time of sealing, in both systems, the resulting pressure value is compromised. At the instantaneous moment of sealing, the pressure value can only be equal to ambient pressure. Following capping there is a subsequent rise in internal pressure as the nitrogen continues to expand but cannot escape the sealed container. However, as the nitrogen is dosed prior to sealing there is a loss of some of the nitrogen dose prior to sealing, the amount of which varies according to many factors. This leaves the process inexact in terms of identifying the dose actually in the container after sealing. It is accepted that this will always be a value less than the dose introduced to the open container prior to sealing.
Because air is composed of 78% nitrogen by volume, nitrogen is abundant. Liquid nitrogen has a boiling point of −320° F. (−196° C.) at atmospheric pressure. Handling liquid nitrogen when pressurizing or inerting food and beverage containers on a production line poses challenges. To use liquid nitrogen injection, a production facility must have a storage vessel, liquid nitrogen piping and an injection device capable of metering small amounts of liquid nitrogen accurately and consistently. To store, transfer or inject liquid nitrogen, insulated equipment is a necessity because liquid nitrogen will boil away rapidly when exposed to room temperatures.
The use of nitrogen, however, does provide for a build-up of internal pressure within a container following capping. This is more practical in the case of beverages filled into the container cold, than when used in conjunction with hot fill beverages. In both cases it is possible that all dosed nitrogen disperses prior to sealing the container, for example if there is a stoppage on the line post dosing and prior to capping. However, in a cold filled application the result would be a container that at least is capped at ambient pressure and will remain at ambient pressure. While the benefit of increased top load and sidewall strength would be lost, the result is not particularly damaging as the container would still look attractive to the consumer when purchased. In the case of a hot filled beverage, however, an insufficient dose results in the container being sealed at ambient pressure and possessing little ability to pressurize the container following sealing. As the liquid contents of the container subsequently cool and contract a vacuum will build and the container will distort as a result. This is not attractive for the consumer. Additionally, the dosing process becomes even more difficult to control in the hot fill environment, particularly at fast line speeds. When nitrogen is introduced into a container under ambient pressure conditions and on top of a heated liquid, the nitrogen will be much more volatile than if the liquid is cold. It will disperse much more quickly prior to capping or sealing leaving the consistency of dose, much more uncertain. A stoppage in the line is therefore more damaging to consistency of dose. For this reason, containers are often overdosed as a precautionary measure, and this is still not ideal.
Plastic bottles need to be pressurized at all line speeds, and if control over the exact pressure achieved inside a container is compromised then the speed of the system will also be compromised in order to correctly pressurise each container.
Food and beverage plant personnel are required to consider a number of goals and criteria when selecting a liquid nitrogen system, including:
-
- Consistent container pressures or consistent oxygen reduction.
- Plant personnel safety.
- Reliable system operation.
- Reasonable acquisition and operating costs.
Each producer has different priorities for each goal, but safety usually is high on the list. It is important to remember that liquid nitrogen becomes a gas at room temperature and expands to 700 times its volume as a liquid. Adequate piping system and injection equipment protection, including safety relief valves, must be used to prevent over-pressurization or equipment rupture. A safety relief valve must be placed between any two shutoff valves in the system. On bulk tank-fed systems, the lowest rated relief device typically is placed outdoors. If a safety relief valve does relieve, it is safer if it happens outdoors rather than inside where someone could get hurt.
Reliability is important on a production line where losses are calculated in minutes of downtime. A liquid nitrogen dosing device will need some startup time from a room temperature condition because all internal surfaces must be cooled down to liquid nitrogen temperatures. As with any liquid nitrogen equipment, operating procedures must be adhered to because the danger of contaminating the equipment with moisture does exist. Moisture is the biggest enemy of the cold surfaces of liquid nitrogen equipment. It takes only a small amount to freeze up the equipment internally. Equipment adjustments such as nozzle changes for different container sizes and maintenance must be able to be completed without moisture contamination or long downtimes. Each production facility has different specifications for liquid nitrogen delivery. Some applications require that the liquid nitrogen be delivered aseptically. In such a case, the dosing unit also must be capable of being sterilized.
Consistent pressurizing or inerting results are important to the entire operation. A water bottle with too little pressure could collapse when stacked or not labelled properly. A bottle with too much pressure possibly could burst when stored in the trunk of a car due to temperature effects. Inerted products could oxidize or spoil if the liquid nitrogen dose was too small; too large a dose on an inerted product could cause an over-pressurized container to jam the production line. Nitrogen injection can be accomplished by dosing individual containers or with a steady stream of liquid nitrogen. Either method can yield consistent results.
Liquid nitrogen will boil away rapidly once it is introduced into a container. Therefore, it is important to control the liquid nitrogen efficiently before dosing. A typical 18 fl oz (600 ml) polyethylene terephthalate (PET) bottle with a 1 fl oz (30 ml) headspace and pressure specification of 17 psig will need approximately 0.001411 oz (0.04 g) of liquid nitrogen. The dose of liquid nitrogen will boil away and expand to 1.163 fl oz (34.4 ml) of room temperature nitrogen gas after the container is sealed. Add 1.163 fl oz of gas to a sealed volume of 1 fl oz, and you end up with 17 psig.
The challenge for the liquid nitrogen dosing equipment manufacturer is to control the boiling liquid and deliver the 0.001411 oz consistently at speeds from 40 bottles/min to more than 1,000 bottles/min. The dosing equipment can control the liquid nitrogen up to the dosing point, but it cannot control the liquid nitrogen's behavior once it has been dosed into the container. The liquid nitrogen will boil away rapidly as the container travels to the capper or seamer, so travel time should be minimized for accurate results. The transfer from dosing to capping also should be smooth to prevent the boiling liquid from bouncing out of the container.
Another aspect to consider is consistent container fill levels. If container headspace varies because the fill levels are wildly different, the final bottle pressures also will be wildly different. For example, suppose the bottle previously mentioned had an 18 fl oz fill with a 1 fl oz headspace, and the next bottle on the production line had a fill of 18.3 fl oz (610 ml) with a 0.6 fl oz (20 ml) headspace. Both bottles receive a 0.001411 oz charge of liquid nitrogen. The liquid nitrogen dosing is consistent; however, in accordance with basic gas laws, the final bottle pressure on the 18 fl oz fill is 17 psig and the bottle with a 18.3 fl oz fill has 25.5 psig final pressure. Many factors determine final bottle pressure accuracy in addition to the dosing equipment accuracy. They include container volume consistency and good sealing closures. All factors must be addressed for good results.
Costs are a critical concern for manufacturers. It is important to remember that initial purchase price, installation expenses and operating costs must be considered jointly. Outside bulk storage tank vessels are more expensive to obtain than small portable dewars, but liquid nitrogen costs much less in bulk than dewars. The changing out process also adds to the hidden cost of using dewars; a 41.6 gal (160 l) dewar usually will last one 8-hr shift on a production line.
Piping is another area where processors try to save money. Most manufacturers can make a relatively inexpensive foam-insulated pipe. However, consider how much liquid nitrogen is lost during one year with a foam insulated pipe. Acquisition and installation costs are higher for a vacuum-jacketed system, but the reduced loss rate due to superior insulation makes operating costs lower than with a foam-insulated system. An inexpensive foam insulated liquid nitrogen injection device is not a bargain if downtime due to a frozen dosing device occurs.
Some dosing devices require a thaw out period of up to 24 hr after use. Startup and shutdown times also are important factors to consider when calculating liquid nitrogen injection system operating costs. When considering liquid nitrogen dosing on a production line, it is necessary to look at many factors. Initial cost is only a small part of the puzzle. Most production plants considering using liquid nitrogen need the proper information and training to be successful and should consult a liquid nitrogen dosing equipment-manufacturer before making a final decision.
The amount of liquified gas added to a container and the head-space volume above the product filled into the container are critical elements in determining the resulting internal pressure of a container upon expansion of the liquified gas. Also, the temperature of hot filled products affects the internal pressure after cooling, according to Boyles law.
Conventionally, the dosage of liquified gas dispensed into a container is based on an average expected fill level of the containers in a continuous fill operation. Using this method, any variation in head-space volume due to variations in fill level would cause under and over pressurized containers. U.S. Pat. No. 4,662,154 discloses the art of providing a closed loop control circuit between a liquid nitrogen dispenser and a pressure detector. The average internal pressure of recently sealed containers is monitored to adjust the dosage of liquid nitrogen added to containers being presently dosed. Containers not meeting the preset pressure range may be rejected.
Problems of uniform pressurization still remain using this method due to basing the dosage on the average pressure of already sealed containers. Whether a given container has a head-space volume that varies high or low, it will receive a dosage based upon an average head-space volume of containers previously sealed. Therefore, the range of container pressures can still vary widely.
Additional problems are caused by the fact that container pressure is the only monitored dosage criteria. Container pressure is measured after a container has already received a dosage and is sealed. This after-the-fact detection can result in high spoilage rates when there are sudden variations in product fill level. These sudden variations will not be detected until after the containers are sealed. Even more spoilage may result as the detection and correction of improper dosages is slow due to the averaging process. Containers must continue to be incorrectly dosed until the average values detect fluctuation.
All of the abovementioned concerns are even greater when used with hot filling liquids into containers.
So called ‘hot fill’ containers are well known in prior art, whereby manufacturers supply PET containers for various liquids which are filled into the containers and the liquid product is at an elevated temperature, typically at or around 85 degrees C. (185 degrees F.).
The container is manufactured to withstand the thermal shock of holding a heated liquid, resulting in a ‘heat-set’ plastic container. This thermal shock is a result of either introducing the liquid hot at filling, or heating the liquid after it is introduced into the container.
Once the liquid cools down in a capped container, however, the volume of the liquid in the container reduces, creating a vacuum Within the container. This liquid shrinkage results in vacuum pressures that pull inwardly on the side and end walls of the container. This in turn leads to deformation in the walls of plastic bottles if they are not constructed rigidly enough to resist such force.
Typically, vacuum pressures have been accommodated by the use of vacuum panels, which distort inwardly under vacuum pressure. Prior art reveals many vertically oriented vacuum panels that allow containers to withstand the rigors of a hot fill procedure. Such vertically oriented vacuum panels generally lie parallel to the longitudinal axis of a container and flex inwardly under vacuum pressure toward this longitudinal axis.
In addition to the vertically oriented vacuum panels, many prior art containers also have flexible base regions to provide additional vacuum compensation. Many prior art containers designed for hot-filling have various modifications to their end-walls, or base regions to allow for as much inward flexure as possible to accommodate at least some of the vacuum pressure generated within the container.
Even with such substantial displacement of vacuum panels, however, the container requires further strengthening to prevent distortion under the vacuum force.
The liquid shrinkage derived from liquid cooling, causes a build up of vacuum pressure. Vacuum panels deflect toward this negative pressure, to a degree lessening the vacuum force, by effectively creating a smaller container to better accommodate the smaller volume of contents. However, this smaller shape is held in place by the generating vacuum force. The more difficult the structure is to deflect inwardly, the more vacuum force will be generated. In prior art proposals, a substantial amount of vacuum may still be present in the container and this tends to distort the overall shape unless a large, annular strengthening ring is provided in horizontal, or transverse, orientation typically at least a ⅓ of the distance from an end to the container.
The present invention relates to hot-fill containers and may be used by way of example in conjunction with the hot fill containers described in international applications published under numbers WO 02/18213 and WO 2004/028910 (PCT specifications) which specifications are also incorporated herein in their entirety where appropriate.
The PCT specifications background the design of hot-fill containers and the problems with such designs that were to be overcome or at least ameliorated and in particular the use of pressure compensation elements.
A problem exists when locating such transversely oriented panels in the container side-wall, or end-wall or base region, even after vacuum is removed completely from the container when the liquid cools down and the panel is inverted. The container exits the filling line just above a typical ambient temperature, and the panel is inverted to achieve an ambient pressure within the container, as opposed to negative pressure as found in prior art. The container is labelled and often refrigerated at point of sale.
This refrigeration provides further product contraction and in containers with very little sidewall structure, so-called ‘glass look-a-like’ bottles, there may therefore be some panelling that occurs on the containers that is unsightly. To overcome this, an attempt is made to provide the base transverse panel with more extraction potential than is required, so that it may be forced into inversion against the force of the small headspace present during filling. This creates a small positive pressure at fill time, and this positive pressure provides some relief to the situation. As further cool down occurs, for example during refrigeration, the positive pressure may drop and may provide for an ambient pressure at refrigerated temperatures, and so avoid panelling in the container.
This situation is very hard to engineer successfully, however, as it depends on utilising a larger headspace in order to compress at base inversion time, and it is less desirable to introduce a larger headspace to the container than is necessary in order to retain product quality.
While it is desirable to have the liquid level in the container drop, to avoid spill when opened by the consumer, it has been found that providing too much positive pressure potential within the base may cause some product spill when the container is opened, particularly if at ambient temperatures.
In most filling operations, containers are generally filled to a level just below the containers highest level, at the top of the neck finish.
Maintaining as small a container headspace as possible is desirable in order to provide a tolerance for subtle differences in product density or container capacity, to minimize waste from spillage and overflow of liquids on a high-speed package filling line, and to reduce container contraction from cooling contents after hot fill.
Headspace contains gases that in time can damage some products or place extra demands on container structural integrity. Examples include products sensitive to oxygen and products filled and sealed at elevated temperatures.
Filling and sealing a rigid container at elevated temperatures can create significant vacuum forces when excessive headspace gas is also present.
Accordingly, less headspace gas is desirable with containers filled at elevated temperatures, to reduce vacuum forces acting on the container that could compromise structural integrity, induce container stresses, or significantly distort container shape. This is also true during pasteurization and retort processes, which involve filling the container first, sealing, and then subjecting the package to elevated temperatures for a sustained period.
Those skilled in the art are aware of several container manufacturing heat-set processes for improving package heat-resistant performance. In the case of the polyester, polyethylene terephthalate, for example, the heat-setting process generally involves relieving stresses created in the container during its manufacture and to improve crystalline structure.
Typically, a polyethylene terephthalate container intended for a cold-fill carbonated beverage has higher internal stresses and less crystalline molecular structure than a container intended for a hot-fill, pasteurized, or retort product application. However, even with containers such as described in the abovementioned PCT specifications where there is little residual vacuum pressure, the neck finish of the container is still required to be very thick in order to withstand the temperature of fill.
My PCT patent specification WO 2005/085082 describes a previous proposal for a headspace displacement method which is incorporated herein in its entirety where appropriate by way of reference.
Where reference in this specification is made to any prior art this is not an acknowledgment that it forms part of the common general knowledge in any country or region.
OBJECTS OF THE INVENTIONIn view of the above, it is an object of one possible embodiment of the present invention to provide a container and contents combination having an increased pressure within an unsealed container whereby the volume of the contents combination exceeds the volume of the as-moulded container, said container having an increased pressure when subsequently sealed or capped.
It is a further object of one possible embodiment of the present invention to provide a container, cap and contents combination that provides for an increased pressure within a sealed container whereby the volume of the contents combination is larger than the contents combination initially filled and sealed within the container, when the contents combination is held at the temperature used at the time of filling and sealing the container.
It is a further object of the present invention to force additional contents into the container under controlled pressure to reinforce the sidewalls.
In view of the above, it is an object of one possible embodiment of the present invention to provide a pressure sealing method and headspace modification method that can provide for increased pressure within the sealed container such that there is increased top load capability.
It is a further object of one possible embodiment of the present invention to provide a pressure sealing method and headspace modification method that can provide for increased pressure within the sealed container such that there is increased top load capability, utilising a gas other than nitrogen such as simple clean or filtered air.
It is a further object of one possible embodiment of the present invention to provide a pressure sealing method and headspace modification method that can provide for removal of vacuum pressure such that there is substantially no remaining force within the container utilising a gas other than nitrogen, such as simple clean or filtered air.
It is a further object of one possible embodiment of the present invention to provide a pressure sealing method and headspace modification method that can provide for removal of vacuum pressure such that there is substantially no remaining force within the container utilising a simple heated liquid such as water.
It is a further object of one possible embodiment of the present invention to provide a headspace compression method whereby air, or some other gas or liquid or combination thereof, is charged into the headspace under sealed pressure to create an increased pressure in order to negate the effect of vacuum pressure created during cooling of the product.
It is a further object of one possible embodiment of the present invention to provide a headspace modification method whereby sterile or heated liquid, or air, or some other gas or combination thereof, is charged into the headspace under sterile conditions to create a positive pressure in order to negate the effect of vacuum pressure created during cooling of the product.
It is a further object of one possible embodiment of the present invention to provide a headspace modification method whereby sterile air, or some other gas or liquid or combination thereof, is charged into the headspace under sealed pressure to negate the effect of vacuum pressure created during cooling of the product.
It is a further object of one possible embodiment of the present invention to provide a headspace modification method whereby a compressive seal is applied to the neck finish of the container.
It is a further object of one possible embodiment of the present invention to provide a headspace displacement method whereby a compressive seal is applied to the neck finish that is forcibly displaceable into the container prior to cooling the liquid contents, such that a positive pressure may be induced into the container.
A further and alternative object of the present invention in all its embodiments, all the objects to be read disjunctively, is to at least provide the public with a useful choice.
SUMMARY OF THE INVENTIONThe pressure sealing method of the present invention may provide for the seal of a container to be finally closed within an increased pressure environment rather than at ambient pressure. In this way an exact pressure can be achieved within the container at the moment of sealing, ensuring consistency of headspace pressure in every container. This prevents any variability caused by inconsistent timing of bottle presentation to a capper, inconsistent fill levels within a container, inconsistent container sizes and so forth.
The present invention may improve upon dosing techniques for expanding gases such as nitrogen, by ensuring the seal is finalised only when the correct dose is applied inside the container.
The present invention may also provide for the use of non-expanding gases to be used, such as air, filtered air, steam or other inert gas.
The present invention may also provide for fluid or liquid to be introduced under pressure into the headspace of a container as opposed to expanding or non-expanding gas. The liquid may be either, heated and contractible or heatable and non-contractable.
The present invention may be suitable for cold filled and aseptic filling lines as a way of controlling nitrogen dosing into containers for increased top load to ensure consistent dose application.
The present invention may be suitable for cold filled and aseptic filling lines as a way of increasing top load in containers but avoiding the use of nitrogen by instead increasing the pressure within containers through the introduction of some other medium, for example filtered air or water, which may be sterile and/or heated and/or cold.
The present invention may provide for the pressure to be increased within the container immediately prior to and during capping.
The present invention may provide for the pressure re-sealing of a container that has been initially sealed in a conventional, ambient pressure manner.
The present invention may provide for pressurisation of the container to provide compensation for any cooling of heated contents within the container, either before or after the contents have cooled.
The pressure sealing method of the present invention may provide for on-line gaseous or liquid dosage calibration in a conventional container filling line. The amount of pressure within the headspace may be controlled precisely at the time of sealing and may be readily adjusted to deliver consistent dosage to each container which corresponds to the container's individually measured head-space volume.
The system may generally include an empty container in-feed station, a continuous container conveying system, a container product fill station, a container head-space dosing station, an optional liquified gas dispensing station, an optional gas dispensing station, an optional liquid dispensing station, a container sealing station, a container internal pressure sensing station, a discharge conveyor and a reject apparatus.
One preferred embodiment of the present invention may provide for the container sealing station to incorporate the optional gas, liquefied gas, liquid and container internal pressure sensing stations.
The system may provide for the on-line control of the head-space volume of each container after it has been filled with product and following the addition of liquid or gas. The head-space volume measurement may be precisely controlled at the time of sealing so that the dosage of liquid or gas delivered to each container may correspond directly to its individually measured head-space, and generally does not alter once immediately sealed, except for variations caused by temperature changes within the contained liquid.
With dosages being exactly correlated to the individually measured requirements of each container, very uniform pressure ranges may be obtained opposed to dosages based on expected fill levels or after-the-fact average measurements. Therefore, containers can be down gauged as they will not be required to accommodate a wide pressure range. Furthermore, the system may achieve lower spoilage rates due to improperly pressurized containers because the system immediately self adjusts for fill variations as containers receive a dosage of liquid or gas.
A particular advantage of the present method and system may be the greater and more precise control allows for much lower pressure dosing for hot fill containers. In prior methods a minimum pressure value can only be assured by over pressurisation on average, such that the lowest dose achieved will meet specifications. This has resulted in generally high pressures achieved during the early stages of hot fill, when the container is hot and malleable. As a result the container is stressed significantly in most occasions, necessitating the need for example for petaloid bases and container designs more suitable to carbonated or pressure vessels. This reduces significantly the design options available for containers, and requires additional weight in the container surrounding the base in order to achieve reasonable results.
Other advantages and aspects of the invention will become apparent upon making reference to the specification, claims, and drawings to follow.
According to one aspect of the present invention there is provided a container for use in hot or cold filling operations and having a seal or cap adapted to provide a temporary opening or aperture into said container, said opening or aperture providing for the introduction under pressure of one or more liquids and/or gases, said seal or cap providing with a neck of said container, in use, a container headspace having a pressure, substantially at the moment of sealing, greater than existed prior to introduction of said one or more liquids and/or gases.
According to a further aspect of the present invention there is provided an expandable container having a seal or cap that is applied to the container under an increased pressure environment such that the container headspace has a positive pressure value substantially at the exact moment of sealing to provide for increased pressure inside the container.
According to a further aspect of the present invention there is provided a container having a seal or cap that is applied to the container under an increased pressure environment such that the container headspace has a positive pressure value substantially at the exact moment of sealing to provide for increased pressure inside the container to negate the effects of a subsequent cooling of a liquid that is heated either before or after filling into the container.
According to a further aspect of the present invention there is provided a container having a seal or cap that is finally closed on a container under a controlled environment such that the container headspace has a controlled pressure value substantially at the exact moment of sealing to provide for increased pressure inside the container to negate the effects of a cooling of a liquid that is heated either before or after filling into the container.
According to a further aspect of the present invention there is provided a capping unit that seals the open end of a container from the outside environment and applies pressure to the inside of the container prior to and during application of a cap or seal such that the container headspace has a positive pressure value substantially at the exact moment of sealing to provide for increased pressure inside the container.
According to a further aspect of the present invention there is provided a capping unit that seals the open end of a container from the outside environment and applies pressure to the inside of the container prior to and during application of a cap or seal such that the container headspace has a positive pressure value substantially at the exact moment of sealing to provide for increased pressure inside the container to negate the effects of a subsequent cooling of a liquid that is heated either before or after filling into the container.
According to a further aspect of the present invention there is provided a container having a seal or cap having a temporary opening or aperture into said container, said aperture providing for the introduction under pressure of a gas, or liquid or both, said aperture also being sealable under compression to provide a controlled raising of internal pressure within the container prior to cooling of the heated contents.
According to a further aspect of the present invention there is provided a container having a seal or cap temporarily applied such that an opening or aperture into said container is provided by an incomplete seal being formed between the cap and the neck finish of the container, said aperture providing for the introduction under pressure of a gas, or liquid or both, said aperture also being sealable under torque compression to provide a controlled raising of internal pressure within the container prior to cooling of the heated contents.
According to a further aspect of the present invention there is provided a container having a seal or cap providing a temporary seal immediately post-filling and an aperture or opening being accessible under sterile conditions to provide for the introduction of a heated or sterile gas, or liquid or both, said aperture or opening also further being sealable under sterile conditions to provide a controlled raising of internal pressure within the container following cooling of the heated contents.
According to a further aspect of the invention a method of filling a container with a liquid includes introducing the liquid through an open end of the container, providing a seal or cap having, or adapted to have, an opening or aperture, providing at least one gas and/or liquid through the opening or aperture and sealing the opening or aperture to increase the pressure in a headspace of the container.
According to a further aspect of the invention a method of filling a container with a fluid includes introducing the fluid through an open end of the container so that it, at least substantially, fills the container, heating the fluid before or after its introduction into the container, providing a seal or cap having an opening or aperture, said opening or aperture being initially sealed, providing for the heated contents to cool, providing a method of subsequently accessing the opening or aperture under controlled conditions and injecting gas and/or liquid through the opening or aperture and sealing the opening or aperture under controlled conditions, so as to compensate for the pressure reduction in the headspace of the container following the cooling of the heated contents.
According to a further aspect of the present invention there is provided a container having an upper portion with an opening into said container, said upper portion having a neck finish adapted to include, subsequent to the introduction of a heated or heatable liquid into the container, a moveable seal, said seal being inwardly compressible or mechanically moveable while the liquid is in a heated state, or prior to heating, so as to increase the pressure of the headspace.
According to a further aspect of the invention a method of filling a container with a fluid includes introducing the fluid through an open end of the container so that it, at least substantially, fills the container, heating the fluid before or after its introduction into the container, providing a moveable seal for the open end to cover and contain the fluid, said seal being capable of mechanical compression of the headspace of the container so as to compensate for subsequent pressure reduction in a headspace of the container under the seal as the heated contents are cooled.
According to a further aspect of the invention a method of sealing a container with a gas or liquid includes capping the container with the entire capping station being pressurised.
Further aspects of the invention which should be considered in all its novel aspects will become apparent from the following description.
The following description of preferred embodiments is merely exemplary in nature, and is in no way intended to limit the invention or its application or uses.
As discussed above, to accommodate vacuum forces during cooling of the contents within a heat set container, containers have typically been provided with a series of vacuum panels around their sidewalls and an optimized base portion. The vacuum panels deform inwardly, and the base deforms upwardly, under the influence of the vacuum forces. This prevents unwanted distortion elsewhere in the container. However, the container is still subjected to internal vacuum force. The panels and base merely provide a suitably resistant structure against that force. The more resistant the structure the more vacuum force will be present. Additionally, end users can feel the vacuum panels when holding the containers.
Typically at a bottling plant the containers will be filled with a hot liquid and then capped before being subjected to a cold-water spray resulting in the formation of a vacuum within the container that the container structure needs to be able to cope with. The present invention relates in one embodiment to hot-fill containers and a method that provides for the substantial removal or substantial negation of vacuum pressure. This allows much greater design freedom and light weighting opportunity as there is no long& any requirement for the structure to be resistant to vacuum forces that would otherwise mechanically distort the container.
As seen in a Prior Art solution in
Referring to
However, as disclosed in the Prior Art as illustrated in
In this way mechanical compression can achieve a positive pressure while the contents of the container are in a heated state, and to subsequently enable the container to be cooled without panelling. The cap components that enter the container headspace under compression will be sterilised therefore by the heated contents prior to cooling. It will be appreciated that many different structures are envisaged for providing a primary sealing structure that is forcible downwards to displace the liquid contents to a large degree. Containers of the 600 ml size for example will require displacement to the order of 20-30 cc of liquid. Containers of the 2000 ml range of size will require displacement to the order of 70 cc of liquid.
It is envisaged that the cap 8 may be of metal or plastics and could in alternative embodiments be pushed into the neck of the container 1 rather than screwed and could be lockable in a required position.
The cap 9 may be controllably displaced downwardly by any suitable mechanical or electrical or other means, or manually.
The method of the present invention allows many variables in mechanical compression to be accounted for, but for larger containers where significant downward displacement would be required it is envisaged that only some of the compressive force would be obtained from a compressive cap and, more significantly, the remainder would be obtained by the methods discussed in the following disclosure.
Referring to
According to a further aspect of the present invention, and referring to
As seen in
As an alternative to the injection of gas, a heated liquid could be injected, for example heated water. This would provide further advantage, in that the liquid injected would not be subject to the expansion that would normally occur when injecting gas into a heated environment. Thus less force would be ultimately applied to the sidewalls of the container during the early hot-fill stages.
Even further, the injected liquid would contract less than a gas when subsequently cooled. For this reason less liquid is necessarily required to be injected into the headspace to provide compensation for the anticipated vacuum forces that would otherwise occur.
Now referring to
As can be seen in
At this point, and as can be seen in
As shown in
Importantly, however, once the contents are cooled there is no residual vacuum in the container.
As an alternative, and as shown in
A further example of such an alternative is provided in
With reference to
As an alternative, the headspace modification unit 102 could also perform the usual function of a typical capping machine. The unit could receive empty containers, apply caps containing the plugs and subsequently torque the caps into position as well as pressurise the container prior to ultimately sealing the container through advancing the plug or some other sealing method.
Still further examples of alternative embodiments of the present invention are illustrated in
A further alternative for a suitable plug mechanism within a cap 80 is illustrated in
The same method procedure may occur using a more typical ‘push-pull’ type sport closure as illustrated in similar manner in
As a further alternative to the present invention, and to remove the need for a hole or plug mechanism within the cap itself, and with reference to
It will be appreciated that the present invention offers multiple choices in carrying out a headspace modification procedure by way of modifying a typical capping machine. Such a piece of machinery could easily be employed to also provide the function of capping the container in addition to modifying the headspace during the procedure.
In facilitating the present invention, the complete or substantial removal of vacuum pressure by displacing the headspace prior to the liquid contraction now results in being able to remove a substantial amount of weight from the sidewalls due to the removal of mechanically distorting forces.
According to a further aspect of the present invention, and referring to
As seen in
As seen in this preferred embodiment of the present invention, in order to remove the vacuum pressure a sealing chamber 84 is applied over the neck finish and cap combination to seal the communicating seal 91 from the outside air (the upper, closed end of the structure 84 is not shown).
Following the introduction of a sterilising medium 66, for example by way of injecting heated water, preferably above 95 degrees C., or a mixture of heated water and steam, the sterilising medium provides for the sterilisation of the internal surfaces of the sealing chamber (84) and the communicating seal 91.
Now referring to
As can be seen in
The integrity of the product volume within the container is not compromised as the environment above the cap has been sterilised prior to communicating with the headspace, and the additional liquid supplied into the container replaces the volume ‘lost’ due to shrinkage of heated liquid within the container prior to the method of headspace replacement described.
Following the pressure equalization, and now referring to
The sealing chamber may now provide for withdrawal of the delivery device 83 which may now be done following a release of sterilising medium and/or pressure within the chamber as the container is ejected and returned to the filling line.
It will be appreciated that many variations of sealing chamber may be utilised, for example the sealing chamber may only seal directly to the top surface of the cap, rather than enclosing the entire cap.
It will also be appreciated by those skilled in the art that may forms of seal may be employed to provide the same the temporary seal and also the plug mechanism to be utilised.
Thus a method of compensating vacuum pressure within a container is described. Referring to
With reference to
Unlike as described in prior art, the present invention provides for the hot liquid within the container to sterilize the underside of the internally presented surface of the inner chamber 9 as it has been compressed into the hot liquid contents.
Ordinarily, as the product cools, a vacuum will build up within the container in the primary headspace 23b under the cap. This vacuum may distort the container 1 to a degree if the walls are not rigid enough to withstand the force.
However, as the internal pressure has been adjusted upwardly prior to product cooling, the net effect may be a temporary raised level of pressure during product cooling and substantially no pressure once product cooling has finished, or perhaps even advantageously a small amount of positive pressure.
Referring to
Referring to
Referring to
The system may also contain a continuous container conveying system, a container product fill station, a container head-space dosing station, an optional liquified gas dispensing station, an optional gas dispensing station, an optional liquid dispensing station, a container sealing station, a container internal pressure sensing station, a discharge conveyor and a reject apparatus.
Alternatively, as illustrated in
The system provides for the on-line control of the head-space volume of each container as it is filled with product through elevated ambient pressure around the container opening. The head-space volume measurement is precisely controlled at the time of sealing so that each container corresponds directly to its individually measured head-space, and generally does not alter once immediately sealed, except for variations caused by temperature changes within the contained liquid and ambient temperature or pressure changes.
With dosages being exactly correlated to the individually measured requirements of each container, very uniform pressure ranges are obtained as opposed to dosages based on expected fill levels or after-the-fact average measurements. Therefore, containers can be down gauged as they will not be required to accommodate a wide pressure range. Furthermore, the system achieves lower spoilage rates due to improperly pressurized containers because the system immediately self adjusts for fill variations.
A particular advantage of the present method and system is the greater and more precise control allows for much lower pressure dosing for hot fill containers. In prior methods a minimum pressure value can only be assured by over pressurisation on average, such that the lowest dose achieved will meet specifications. This has resulted in generally high pressures achieved during the early stages of hot fill, when the container is hot and malleable. As a result the container is stressed significantly in most occasions, necessitating the need for example for petaloid bases and container designs more suitable to carbonated or pressure vessels. This reduces significantly the design options available for containers, and requires additional weight in the container surrounding the base in order to achieve reasonable results.
With reference to
When a PET container is filled with liquid at a temperature above 70 degrees Celsius the plastic walls become very soft and elastic as the material passes its elastic modulus. With the subsequent force being applied to the container by introduction of a force to raise internal pressure, the sidewalls expand and the overall volume of the container increases. Some of this increase in volume is non-recoverable and results in the container becoming larger than originally manufactured. A particular object of the present invention is to reduce the amount of stress being applied to the sidewalls to the lowest possible amount to prevent unnecessary volume growth in the container.
This is of particular benefit when utilising very thin sidewalls such as found in lightweight containers. It will be appreciated therefore, that in a particular volume size container to be filled with a heated liquid, for example in a range of 75 to 95 degrees Celsius, then the amount of gas or fluid required to be introduced to compensate for the subsequent contraction of contents may be reduced if the container has a residual capacity to account for a portion of the expected contraction. For example, in a container of 600 cc size, it may be expected that approximately 25-30 cc of fluid contraction may occur and therefore an amount of gas or fluid equivalent to this would need to be injected into the headspace during final sealing of the container in order to compensate. By providing this compensation it may be possible to therefore lightweight the container or change the shape of the container as there is a much reduced need for the container to resist vacuum pressure forces that would otherwise occur.
It will be appreciated that introduction of this additional material creates extra stresses initially on the container. By configuring at least a portion of the sidewall to respond to vacuum forces, it is possible to reduce the amount of initial material introduced, for example to 50% of the required amount, if the sidewalls are able to provide compensation for 50% of the required amount also.
It will be appreciated that a container-that is only required to compensate for 50% of expected vacuum pressure through sidewall compensation will be able to be made more lightweight than a container required to compensate for the entire 100% through sidewall compensation.
With reference to
With reference to
With reference to
With reference to
With reference to
Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated as if individually set forth.
Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope or spirit of the invention.
Claims
1-12. (canceled)
13. A sealing machine apparatus for pressurizing the headspace of a filled container while applying a seal, comprising: an apparatus for receiving a plurality of containers; a pressure chamber apparatus connected to a surface or sealing member for engaging a surface on the container or on a cap provided for the container; a source of pressure or dosing system coupled to said pressure chamber for raising the pressure within said pressure chamber and said containers; apparatus for moving the sealing member or surface into engagement with the surface on the container or cap; said pressure chamber surrounding a container sealing apparatus for applying a seal or said cap to at least one of said containers; said container sealing apparatus moving to seal said container within the pressure chamber while the pressure chamber is subjected to a raised internal pressure to create an increased pressure within the sealed container.
14. An apparatus as claimed in claim 13, wherein said sealing machine is a capping machine, and said seals are said caps or are closures.
15. An apparatus as claimed in claim 13, wherein said containers are filled with a heated liquid.
16. An apparatus as claimed in claim 13, wherein said sealing machine is a rotary device driven by a rotatable driven turret.
17. An apparatus as claimed in claim 16, wherein said containers are moved about in a generally circular path by said turret.
18. An apparatus as claimed in claim 13, wherein said pressure chamber provides temporary sealing of said containers adjacent a neck finish of said containers.
19. An apparatus as claimed in claim 18, wherein said container sealing apparatus or said pressure chamber provides temporary sealing of said containers at or adjacent a neck support ring of said neck finish.
20. An apparatus as claimed in claim 13, wherein said container sealing apparatus is a holding apparatus for holding the cap in position to engage a finish of the container.
21. An apparatus as claimed in claim 13, wherein said container sealing apparatus provides capping torque to close the container.
22. An apparatus as claimed in claim 13, wherein said source of pressure or dosing system provides at least one liquid and/or gas.
23. An apparatus as claimed in claim 22, wherein at least one said liquid and/or gas is steam, air, nitrogen, or carbon dioxide.
24. An apparatus as claimed in claim 13, wherein said containers are for use in hot or cold filling operations each having a said seal or said cap adapted to provide a temporary opening or aperture into said container, said opening or aperture providing for the introduction under pressure of one or more liquids and/or gases, said seal or cap providing with a neck of said container, in use, a container headspace having a pressure, at the moment of sealing, substantially greater than existed prior to introduction of said one or more liquids and/or gases.
25. An apparatus as claimed in claim 24 further including at least one vacuum compensation element in a sidewall of the container.
26. An apparatus as claimed in claim 24 or claim 25 including at least one vacuum compensation element in a base of the container.
27. An apparatus as claimed in claim 24 including at least one expandable element in a sidewall of the container.
28. An apparatus as claimed in claim 24 or claim 27 including at least one expandable element in a base of the container.
29. An apparatus as claimed in claim 24 wherein said greater pressure, substantially at the moment of sealing, is positive.
30. An apparatus as claimed in claim 24 for hot filling wherein, after hot filling, the greater pressure compensates for a pressure reduction on cooling of the contents of the container.
31. An apparatus as claimed in claim 24 wherein said seal or cap is adapted to provide said opening or aperture after said seal or cap has been applied to the neck.
32. An apparatus as claimed in claim 24 wherein said seal or cap is adapted to be pierced to provide said opening or aperture and expose the container headspace to ambient pressure.
33. A cap for a container, the cap being adapted for use with the apparatus of claim 13.
34. A system for filling a container with a fluid including introducing the fluid through an open end of the container, providing a seal or cap, providing a sealing chamber enclosing an opening or aperture between said seal or cap and said container interior, increasing the pressure within the sealing chamber by introducing at least one liquid and/or gas through the opening or aperture to create an increased pressure within the headspace of the container, sealing the opening or aperture within the sealing chamber under the increased pressure conditions.
35. A system for filling a container as claimed in claim 34, in which the fluid is heated before or after its introduction into the container, and said system compensates for subsequent pressure reduction in a headspace of the container under the seal or cap following the cooling of the heated contents.
36. A system as claimed in claim 34 in which the at least one liquid and/or gas passes through the opening or aperture under pressure.
37. A system as claimed in claim 34 in which the container is positioned in a pressurizing area.
38. A system as claimed in claim 34 in which the at least one liquid and/or gas is a heated liquid or steam injected through the opening or aperture.
39. A system as claimed in claim 34 in which the opening or aperture is provided with a temporary or partial seal through which the at least one liquid and/or gas is provided.
40. A system as claimed in claim 35 including conveying said sealed or capped containers prior to the pressure chamber, and creating and/or providing said opening or aperture within the pressure chamber.
41. A system as claimed in claim 40 in which the opening or aperture provided within said seal or cap is provided with a temporary or partial seal for at least a period of time prior to conveyance into said pressure chamber.
42. A system as claimed in claim 41 in which said seal or cap has a liner material on an inside surface, said liner temporarily sealing the opening or aperture.
43. A system as claimed in claim 40 in which the opening or aperture is sealed under elevated pressure conditions.
44. A system as claimed in claim 34 or 40, wherein said container includes at least one moveable pressure panel in a sidewall of said container.
45. A system as claimed in claim 40, wherein said container includes at least one moveable pressure panel in a base of said container.
46. A container when filled by the system of claim 40.
47. A method of filling and processing a container with a fluid including:
- introducing the fluid through an open end of the container so that it, at least substantially, fills the container,
- applying a seal or cap to said container,
- transporting or conveying said container,
- creating and/or providing an opening or aperture in said seal or cap,
- providing a method of introducing at least one liquid and/or gas through the opening or aperture at a pressure greater than within said container prior to providing said opening or aperture,
- providing a method of sealing the opening or aperture.
48. A method as claimed in claim 47 wherein said seal or cap is subjected to at least partial sterilization treatment prior to the provision of said opening or aperture.
Type: Application
Filed: Nov 17, 2010
Publication Date: Dec 13, 2012
Inventor: David Murray Melrose (Mt. Eden)
Application Number: 13/510,881
International Classification: B65B 31/00 (20060101); B65D 51/00 (20060101); B65D 6/40 (20060101); B65B 1/00 (20060101);