Patent Publication Number: US-2013239522-A1

Title: Controlled container headspace adjustment and apparatus therefor

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to a sealing and pressure dosing apparatus and more particularly to a capping and/or sealing apparatus for applying closures to containers at high speed, and even more particularly to a capping apparatus including a pressure dosing system for providing a pressure medium into a head space of each of the containers prior to closure application by the apparatus. The pressure sealing may be undertaken either during the initial sealing of the container, or as a secondary operation after the initial sealing the container. The headspace pressurization increases the internal pressure within the container, providing for increased top-load capability of the container. This invention may further relate to hot-filled and pasteurized products packaged in heat-set polyester containers and for controlling the cooling of any containers filled with a heated liquid. 
     BACKGROUND 
     The present invention in one particular embodiment is directed to a capping apparatus including a pressure dosing system which has been specifically configured to overcome shortcomings associated with previously known arrangements by effecting injection of any medium, for example gas, liquid, steam or any combination into containers essentially at about the time of the application of a closure to each container by the apparatus. 
     In the present specification, including the claims, the term “fluid” covers both liquids and gases unless the context clearly indicates otherwise. 
     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. 
     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. 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. 
     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. 
     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 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. Conventionally, the dosage of liquefied 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. 
     The abovementioned concerns are even greater when used with hot filling liquids into containers. When PET containers are filled with a heated liquid, the bottles are transported through a filling machine by means of a conveying device and a heated liquid is generally introduced to the container. Alternatively, a cool liquid may be introduced that is subsequently heated after the container has been capped or sealed. 
     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. In typical prior art filling situations, containers are filled with a heated liquid above 70° C., and more often subjected to filling temperatures of between 70° C. and 95° C. Once capped, or in other words sealed, the product must be maintained at a certain high temperature for a certain critical time in order to complete the process of pasteurization within the container. Even further, the container must also be inverted or at least tipped sideways for a certain time in order to sterilize the underneath of the seal or cap. 
     It is preferable for example to maintain a temperature of above 80° C. for a 2 minute period after sealing for many beverages prior to starting the cooling process. Therefore the typical cooling of containers to bring them down to around 30° C. does not start until at least some time after the inversion of the container so that the core temperature of the liquid within the container is maintained high enough to sterilize the underneath of the cap and complete sterilization of the internal container contents. 
     Once the cooling process is finally allowed to be deployed on the container it is usually cooled rapidly in a heat exchanger or cooler in order to provide a container that may be subsequently labelled and packed into boxes or the like for transportation away from the filling line. 
     Therefore, in prior art it is not considered feasible to provide cooling simultaneously with the capping of filled containers, or the temperature of the contents is compromised before it may be utilized for internal sterilization purposes. Not only would there be substantial risk in introducing foreign matter into the container prior to sealing, but the temperature of the product would be compromised and the efficacy of the pasteurization model would be corrupted. 
     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. 
     The present invention relates to both cold and 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. 
     Those skilled in the art will be 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. 
     In hot filling of beverages in PET containers, the thermal stability of the material of the container also constitutes a challenge. PET has a low glass transition point of approximately 75 degrees C. When the headspace of a container is pressurized while the liquid contents are above about 70 degrees C., the container walls are subjected to particularly damaging forces. This occurs following the capping of a lightweight container filled with a heated liquid, even when additional pressure is not applied to the container. The build-up of pressure comes from the headspace increasing in temperature immediately following capping and exerting expansion forces against the lightweight surfaces of the container. 
     In the current art for both cold and hot filled beverage applications, the containers may be conveyed through a nitrogen-dosing unit where nitrogen may be dripped into the unsealed bottles and shortly afterwards the bottles are sealed. This method is also referred to as the nitro-dose process. Liquefied gas may be injected by an apparatus such as that disclosed in US Patent Application No. 2005/011580 A1 to Siegler et al., which is incorporated herein by reference in its entirety. Liquefied gas may alternatively be dripped in by an apparatus such as that disclosed in U.S. Pat. No. 7,219,480 to Winters et al, which is also incorporated herein by reference in its entirety. 
     In such nitro-dose applications there is significant container distortion when the PET material is above about 70° C. to 75° C. due to the high level of nitrogen pressure within the container. Such distortion is non-recoverable. The container effectively grows in volume and the base is disfigured and unstable. 
     Also for example, structures in the sidewall, such as ribbing, may be similarly affected causing uncontrolled container growth and distortion. This distortion causes a weakness in any strengthening structures and is very undesirable. 
     Typically, at present, hot closed bottles will be transported to the bottle cooler preferably by means of at least one conveyor belt. In the cooling device or heat exchanger, the hot bottle is cooled down close to room temperature or to around 30° C. to 35° C. 
     Typical hot fill operations utilize ambient water to slowly cool hot filled packages after they are sealed, until they return to ambient temperature. This usually occurs several minutes after the product has been filled into the container, whereby the container walls are subjected to temperatures above the glass transition point of PET. 
     The temperature of the filled contents take a period of time to cool from a typical 85-95 degrees C. of fill temperature to below approximately 60 degrees C. At 60 degrees C. and below the PET does not distort under stress of internal pressure in the way it does above its glass transition point. 
     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 INVENTION 
     It is thus an object of the present invention in its various embodiments to overcome or at least alleviate problems in prior art proposals to the present time. 
     A further and alternative object of the present invention is to at least provide the public with a useful choice. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, there is provided a sealing and pressure dosing apparatus, including a sealing machine including a driven turret for serially receiving a plurality of containers, at least one sealing head for applying seals to said containers as said containers are moved about in a path by said turret, a pressure sealing chamber for isolating a neck finish end of said containers and accessing the headspace of said containers, said pressure sealing chamber providing a pressure dosing system for raising the pressure within said containers received by said sealing machine prior to sealing by a respective seal applied thereto, said pressure dosing system being integrated with the sealing machine. 
     Preferably, a capping and pressure dosing apparatus embodying the principles of the present invention includes a rotary capping machine including a rotatable driven turret for serially receiving a plurality of containers, typically bottles. The apparatus of the present invention includes a pressure dosing system including a sealing chamber which is positioned to isolate and seal the upper neck finish of the containers and the mouth of each container as the container moves through the capping machine. By this arrangement, pressure control is highly optimized, enhancing operating efficiency. In the preferred form, operation of the pressure sealing system is electronically coordinated with operation of the capping machine to facilitate consistent operation, permitting the pressure system to be operated either continually, or intermittently, as desired. 
     Preferably, the rotary capping machine of the apparatus includes a plurality of capping heads for applying closures to respective ones of the containers as the containers are moved about a generally circular path by the rotary turret of the capping machine. The capping machine may be of a generally conventional configuration, with associated rotary conveyors, or starwheels, operatively associated with the capping machine for supplying filled, but unsealed containers to the machine, and for receiving filled and sealed containers from the machine. 
     The pressure dosing system of the present invention is configured for pressurizing the head space of each of the containers received by the capping machine simultaneously with the application of a respective closure thereto. As is known by those familiar with the art, the head space of a container is that upper region of a container which is unfilled with the typically liquid contents of the container. Injection of pressure into this region of containers having non-carbonated contents desirably acts to enhance package for more secure handling, stacking, and dispensing (such as from vending machines) of products, and desirably acts to enhance the freshness and flavor of the package contents if an inert gas such as nitrogen is utilized for example. 
     Significantly, the present apparatus preferably is configured to effect pressure injection at, or in close relationship to, the so-called capping head of the capping machine, that is, the point at which the package is positioned for closure application. As will be appreciated, this is in significant distinction from systems employed heretofore, where nitrogen has typically been injected into containers well before closure application, typically before the containers were even received by a capping machine or where liquid nitrogen has typically been injected into containers under ambient pressure conditions and thus being susceptible to immediate expansion out of the container prior to actual sealing by capping. 
     To this end, the pressure dosing system of the present apparatus preferably includes a pressure sealing chamber connected to the capping head within the circular path about which the containers are moved by the capping machine, at a position over each container and the respective one of the closures held by one of the capping heads. The pressure dosing system includes a control valve to selectively permit intermittent or continuous dispensing of pressure medium, for example highly filtered air or steam, with a control system provided for coordinating operation of the pressure dosing system with operation of the capping machine. 
     The pressure sealing chamber preferably defines a downwardly connecting sealing surface for engagement with either the upper part of each container or the cap of each container. By this configuration of the sealing chamber, pressure medium is directed downwardly through the open mouth of each container as it is being moved by the capping machine, with closure application initiated simultaneously after each container is moved passed the capping head. 
     Turning then to the situation whereby nitrogen liquid is dropped into a hot-filled bottle, it will be appreciated that following capping an immediate and severe increase in both temperature and pressure is experienced against the sidewalls. With the container walls experiencing temperatures of between 85° C. and 95° C. in most situations, and a need to maintain this temperature above 80° C. for up to 2 minutes to complete pasteurization after capping, it will be appreciated that the walls of the container will be severely stressed while above 70° C. in the case of PET as this is the glass transition temperature. 
     The present invention may therefore provide for immediate cooling of the walls of the container, even prior to the rise in internal pressure within the container, and does so in a manner allowing the internal product temperature to be maintained above approximately 80° C. for up to approximately a 2 to 3 minute period. In other words, the present invention in another aspect provides a method of pressurizing a container filled with a heated liquid and controlling a differential temperature between the sidewalls of the container and the internal contents of the container. 
     In this way, the sidewalls may be kept at a temperature below approximately 70° C. in the case of PET, while maintaining a higher internal temperature of between 80° C. and 95° C. 
     According to a further aspect of the present invention there is provided method of filling 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, heating the fluid before or after its introduction into the container, providing a seal or cap, providing an opening or aperture between said seal or cap and said container, providing at least one fluid through the opening or aperture, sealing the opening or aperture under increased pressure conditions, so as to compensate for subsequent pressure reduction in a headspace of the container under the seal or cap following the cooling of the heated contents, and cooling at least a part of outside walls of said containers substantially immediately after sealing or capping said containers. 
     According to a still further aspect of the present invention there is provided a method of filling 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, heating the fluid before or after its introduction into the container, applying a seal or cap to said container, providing an opening or aperture in said seal or cap, providing at least one fluid or gas through the opening or aperture, sealing the opening or aperture, so as to compensate for pressure reduction in a headspace of the container under the seal or cap following the cooling of the heated contents. 
     The present invention may also provide a lower pressure environment within the container immediately after sealing. Typically in a nitrogen dose method, the container will experience pressures of between 15 psi and 30 psi during the first 2 minutes after sealing. In the present invention, the pressure may be modified downwardly to between 1 psi and approximately 8 psi. This significantly reduces internal stresses on the container while the product must be maintained at high temperature to complete pasteurization after sealing. 
     To summarise, in prior art situations, once a heated liquid is filled into the container the material of the container walls, for example Polyethylene Terephthalate (PET), will experience a rapid rise in temperature. Once the material temperature rises above the glass transition value, for example above 70° C. in the case of PET, the sidewalls are subject to severe distortion. This distortion force will be present until the container is able to be cooled to bring the core temperature of the product down to below approximately 70° C. and more typically to approximately 30° C. following a period of time in a cooling heat exchanger. 
     In the current art of filling hot or heated beverages, the bottom and sides of the bottles may be rapidly cooled anywhere in the filling line from the blow moulding machine through to the filling machine and through to the labelling process by means of air or water jets. This process is designed to lower the internal temperature of the container contents. 
     US Patent Application No. 2007/0125742 to Simpson et al., which is incorporated herein by reference in its entirety, describes the step of placing the container in a cooling apparatus after capping. 
     US Patent Application No. 2007/0184157 A1 to Stegmaier, which is incorporated herein by reference in its entirety, describes a process for hot filling and quick chilling a container after capping, in particular to retain maximum flavour profiles following acceptable sterilisation procedure after capping containers. 
     Also well known in the current art is the method of blowing or forcing air onto containers after filling and capping, and often to either cool bottles or dry them. In the case of pressurised containers it is well known that removal of liquid droplets from the surface of the container as quickly as possible removes stress concentration points on the surface of the container. 
     The present invention provides for not only a lowering of internal pressure to below approximately 10 psi, and more preferably to between 5 psi and 10 psi, and even more preferably to between 1 psi and 5 psi, but the present invention may also provide for a method of differentially cooling the outside walls of a container immediately prior to capping or during capping and for a controlled period afterwards to ensure correct product pasteurization and for the sidewalls to be simultaneously protected from excessive force. 
     In the present invention, the pressure is raised within the container to minimal levels, and the cooling process of the container may be started earlier than in prior art. In the present invention the cooling process may be undertaken within the capping or sealing device itself, which has not been described, developed or achieved before in the art. 
     More particularly, in the present invention, the outside shell of the filled container may be temperature controlled to ensure a maximum internal temperature is retained for any given time period, while maintaining a differential temperature on the outside surface or shell. The application of such control allows for some products to be cooled in a minimum time to retain maximum flavour profiles, or to be cooled in maximum time for maximum pasteurisation while maintaining thermal control over the PET container itself. 
     The present invention therefore also preferably provides 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, and with greater control over the structure of the container through the critical high heat and high pressure cycle period within the first few minutes of post filling. 
     With dosages being exactly correlated to the individually measured requirements of each container, very uniform pressure ranges may be 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 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. 
     Preferably, a container having a seal or cap providing a temporary seal immediately post-filling and an aperture or opening being accessible under both ambient or sterile conditions to provide for the introduction of a medium, 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. 
     Preferably, a system and process provides for pressurising the headspace of a container following the introduction of a heated or heatable liquid and sealing the container so that the pressure is retained within the container, and to cool the container sidewalls to a temperature less than the central core temperature of the liquid contents. 
     Preferably, a sealing device raises the pressure inside a container prior to sealing, and applies a cooling method to the container sidewalls for a period of time after sealing until the temperature of the liquid contents fall below a threshold value. 
     Preferably, this is achieved by means of a device for sealing and/or capping containers that can also pressurize containers prior to sealing and/or capping, and that may also preferably initiate the differential cooling process to prevent the sidewall temperature exceeding approximately 70° C. 
     As the containers exit the capper unit, the differential temperature regulation must be maintained until pasteurization is complete within the container, and therefore often through the typical inversion process of the container and for a set period of time afterwards. Once the critical time period is reached to deem pasteurization has been satisfied, then the product temperature may be more aggressively reduced in order to bring the product temperature down to below approx. 70° C. Thus, the process is no longer differential in object, whereby as high an internal temperature as possible is maintained against a cool outer shell of container sidewall. The process may be more aggressive in order to bring the internal temperature down. This period of cooling is the more traditional approach of relatively unregulated cooling application and is found in all prior art process. In the present invention it is preferably mandated to occur, however, until the core temperature of the product has reached below approximately 70° C. In prior art there is no such mandate and the cooling is applied as soon as pasteurization is complete and it is applied until the product is brought down to an exit temperature of approximately 30° C. 
     In the present invention, the cooling may be stopped after the product has decreased in temperature to approximately 60° C. to 70° C. More traditional cooling may be applied at any time after this, and could be up to 10 minutes afterwards in situations where containers are held in collection bays for example. 
     In the present invention the cooling method may be by the use of any typical medium such as water or air. 
     It will be appreciated that in order to maintain as high a core temperature as possible against a shell temperature below 70° C., then it would be preferable to use a water temperature below 70° C. The higher the temperature of the applied medium then the higher the temperature maintenance within the container until pasteurization is complete. The lower the temperature application to the sidewalls then the more danger the internal temperature is reduced too rapidly. 
     It will be further appreciated that in order to save energy cost it is preferable to apply an ambient temperature medium. Therefore in order to maintain correct internal temperatures the flow and application rate of the cooling medium must be carefully controlled to keep internal temperatures high. 
     Notwithstanding this, it will be appreciated that should mediums be applied at more typical cooling temperatures, then these must be very carefully controlled to maintain correct differential between the shell temperature and the core temperature. 
     Further aspects of the invention which should be considered in all its novel aspects will become apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1   a:  shows a side elevational, diagrammatic view of a capping and pressure dosing apparatus embodying some of the principles of one embodiment of the present invention. 
         FIG. 1   b:  shows a plan, diagrammatic view of a capping and pressure dosing apparatus embodying the principles of part of one embodiment of the present invention. 
         FIG. 2 : shows a method according to part of an embodiment of the invention with a Sealing Unit or Capper capable of pressurizing the headspace of a container prior to capping or sealing; 
         FIGS. 3   a - d:  show a container and Sealing Chamber according to part of an embodiment of the invention; 
       FIGS.  4 : a - d  shows a method and Sealing Chamber according to a further embodiment of the invention with a Sealing Unit or Capper capable of pressurizing the headspace of a container; 
         FIG. 5   a - c:  show enlarged views of part of one possible embodiment of the cap of  FIGS. 3   a - c;    
         FIG. 6   a - c:  show part of one embodiment of enclosing the cap of  FIG. 5  with a pressure application device; 
         FIGS. 7   a - c:  show part of one embodiment of a cap-sealing device suitable for use in the pressure application device of  FIG. 6 ; 
         FIGS. 8   a - c:  show part of one embodiment of cap-sealing device of  FIG. 7  closing the cap while under compression; 
         FIGS. 9   a - c:  show withdrawal of the cap-sealing device of  FIG. 8  following sealing and subsequent decompression of the compression chamber; 
         FIGS. 10   a - c:  show the container cap of  FIG. 9  following release from the compression chamber (container not shown fully); 
         FIGS. 10   d - f:  show a part of a further embodiment of the container cap of the present invention; 
         FIG. 11   a - c:  show enlarged views of part of a further embodiment of the cap of  FIGS. 3   a - b;    
         FIG. 11   d - f:  show enlarged views of a further part embodiment of the cap of  FIGS. 3   a - b;    
         FIGS. 12   a - c:  show part of one embodiment of a cap-sealing device suitable for use in the sterilising application device of  FIG. 11 ; 
         FIGS. 13   a - c:  show part of one embodiment of cap-sealing device of  FIG. 12  piercing the cap while under sterilisation; 
         FIGS. 14   a - c:  show withdrawal of the piercing and delivery device of  FIG. 13  following sterilisation and subsequent pressure equalisation of the headspace; 
         FIGS. 15   a - c:  show the resealing of the container cap of  FIG. 14  prior to container release from the sterilisation chamber (container not shown fully); 
         FIGS. 16   a - c:  show additional views of the cap of  FIGS. 12 ,  13 ,  14 ,  15  according to one possible method of headspace modification; 
         FIG. 17 : shows a method according to a further possible part embodiment of this invention; 
         FIG. 18 : shows a further possible part embodiment of the invention using a sealing chamber; 
         FIG. 19   a - b:  show a possible part embodiment of the invention in the form of a sealing machine; 
         FIG. 20  shows diagrammatically a possible capping system; 
         FIGS. 21   a - c;    22   a - c;    23   a - c;    24   a - c;    25   a - c;  and  26   a - c:  shows various possible embodiments with alternative forms of vacuum compensation; 
         FIGS. 27   a - d;  and  FIGS. 28   a - d:  show further alternative embodiments of the invention using a cold  water spray or cold water bath to cool the containers; and 
         FIG. 29  shows a method according to one embodiment of the invention with a Sealing Unit or Capper capable of pressurizing the headspace of a container prior to capping or sealing, optional cooling of the container surface within the Sealing Unit and following release; 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In my further PCT specifications WO 2009/142510 and WO 2011/062512, the contents of which are herein incorporated in their entirety where appropriate, are described headspace modification methods and apparatus therefor. 
     However, in prior art proposals, in order to pressurize containers for both cold and hot filled beverage applications, containers must be conveyed through a nitrogen-dosing unit where nitrogen may be dripped into the unsealed bottles and shortly afterwards the bottles are sealed. 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. 
     While the present invention is capable of various embodiments, there is shown in the drawings and specification some presently preferred embodiments, or parts of presently preferred embodiments, with the understanding that the present disclosures are to be considered as exemplifications of the invention, and are not intended to limit the invention to any specific embodiments illustrated. It will be appreciated that the terms capping and sealing may be used interchangeably at times. 
     With reference to  FIGS. 1   a - b,  a capping and pressure dosing apparatus  102  is disclosed embodying some of the principles of the present invention. As will be further described, the present apparatus includes a rotary capping machine which is configured for high speed application of closures to associated bottles or like containers. As will be recognized by those familiar with the art, this type of machine serially receives filled bottles from an associated in-feed conveyor or so-called star-wheel, with a machine being configured to substantially continuously apply threaded closures to respective ones of the containers as they are moved through the machine about a generally circular path. The closures are typically applied by rotation to inter-engage the screw threads of each closure with its respective container before the container is moved out of the machine and received by an associated output conveyor or star-wheel. While such equipment exemplifies the configuration of the present invention, it is to be understood that the present capping and pressure dosing apparatus can be configured to operate in accordance with the principles of the present invention by use of other, like equipment, including linear or in-line capping machines. 
     The pressure dosing system of the present apparatus may also be generally configured in accordance with known capping systems, such as disclosed in U.S. Pat. No. 7,219,480 to Winters et al, which is incorporated in its entirety by reference. 
     In distinction from arrangements known heretofore, the pressure dosing system of the present system has been electronically integrated within the capping machine to facilitate injection of pressure medium into each of the containers being filled simultaneously with the application of the closure to the container. In accordance with the present invention, this is effected by providing the pressure dosing system within a sealing chamber which is positioned to extend generally over and seal off the upper neck finish or cap of the filled containers as they are moved by the capping machine. 
     With further reference to  FIGS. 1   a - b,  the present apparatus includes a capping machine  102 , as described above. Capping machine  102  is configured to receive containers  1 , such as bottles, from an infeed conveyor or starwheel  66  along a circular path designated “infeed” in  FIG. 1   b,  and to deliver the filled and sealed containers to an output conveyor or starwheel  77  along a circular path designated “output” in  FIG. 1   b.  The capping machine  102  includes a rotatably driven carrier or turret which rotates around a centerline ( FIG. 1   a ) and moves the containers  1  along and about a generally circular path which intersects the circular paths defined by the input and output starwheels  66  and  77 . 
     As the containers  1  are moved about the circular path by the capping machine  102 , the closures  80  are applied to a respective one of the containers. To this end, the capping machine includes a plurality of capping heads  101 . Each of the capping heads  101  is rotatably driven so that a closure  80  received thereby can be positioned above a respective one of the containers  1 , and the closure rotated downwardly onto the container into sealing relationship therewith, closing the container and completing packaging of its contents. 
     As containers  1  are handled by the capping machine  102 , the containers each move along the generally circular path defined by the capping machine from an input point to an output point. As will be recognized by those familiar with the art, the input point is sometimes referred to as the transfer point, that is, the theoretical point at which filled container  1  is positioned for receiving a closure thereon. 
     In accordance with the present invention, pressure dosing with any medium, for example compressed air in  FIG. 1   b,  is effected within a sealing chamber  84  to facilitate consistent dosing of the containers  1 . To this end, the present invention includes a pressure dosing system within operative association with the pressure sealing chamber  84 , which is integrally connected to the capping or sealing head of the capping machine  102 . 
     By this configuration, the pressure sealing chamber is positioned to dispense medium not only to surround and envelope the upper end of the container  1  or cap  80 , but also downwardly directly through the open mouth of each of the containers  1  received by the rotary turret of the capping machine  102  just prior to final application of a closure or seal to each of the containers by one of the capping heads  101 . 
     Not only does the present apparatus provide consistent positioning of the container package for pressurization, the container is substantially stabilized, reducing or eliminating further potential for product spillage, allowing for full pressurization. Additionally, dosing simultaneously with closure application prevents any pressure dissipation. 
     In the preferred form of the present invention, electronic controls are provided which are operatively connected with the electronic controls of the capping machine for accurate timing of the pressure dosing system. The pressure sealing chamber or pressure delivery mechanism supplying the sealing chamber can be provided with a suitable fitting which permits a suitable device to be positioned for controlling and monitoring operation of the system. By electronically controlling the pressure dosing system, and coordinating its operation with the capping machine  102 , the present apparatus provides extremely accurate pressure dosing throughout the entire speed range of the capping machine. 
     Referring to  FIG. 2 , a method of pressurizing containers is illustrated whereby the sealing unit or capper receives the filled containers, subsequently seals the headspace from everything but the internal chamber of a sealing chamber, pressurizes the headspace within the sealing chamber and therefore the headspace within the container, and subsequently seals or caps the container so that a raised pressure exists in the sealed container which is then ejected from the pressure sealing unit. 
     Referring to  FIGS. 3   a - d,  part of an exemplary embodiment of the present invention is shown with a cap  80  engaged with the container neck finish  120 . According to one aspect of the present invention a container  1  may enter a capping or sealing station after being filled with liquid contents such that a headspace exists above the fluid level  40 . The upper neck region of the container is sealed from the ambient environment by a sealing chamber  84  that has a sealing surface  841  in contact with the container. According to the invention, prior to tightening or applying torque to the cap to seal the headspace finally, a pressure is applied within the sealing chamber  84  such that the internal chamber of the container is pressurized, more particularly the headspace above the liquid is pressurized. Once pressurized the cap is tightened down by the capping or sealing station such that the container has a raised internal pressure prior to release from the unit, as seen in  FIG. 3   b.    
     The sealing mechanism may be of many styles, but there is distinct advantage in ensuring the size of the pressure sealing chamber is kept to a minimum. This ensures rapid pressurization of the chamber in high speed rotary situations. 
     In this embodiment it is envisaged that standard caps are applied to the containers and the pressure capping unit applies internal pressure to the container prior to applying caps. 
     The sealing mechanism may be of any style, for example the chamber could seal some distance from the neck finish  120  of the container and down the shoulder region, as illustrated in  FIG. 3   b , or more preferably immediately under the neck support ring  33 , as illustrated in  FIG. 3   c.    
       FIG. 3   d  shows in closer detail one example of a sealing chamber. The chamber is capable of sealing under the neck support ring of a container, and prior to applying a cap. The sealing chamber could be one of many such chambers for example on a rotary system for torque sealing the cap to the container. Sealing under the neck provides for multiple changes in container styling without the need for change parts providing each container has the same neck finish diameters. Further, by providing for support under the neck the container may be raised upwardly and supported in the capper to avoid any top load pressure and to also allow for multiple bottle heights without the need for change parts also. 
     As a further alternative to the present invention, and with reference to  FIG. 4   a  a method of pressurizing containers is illustrated whereby the Pressure Sealing Unit receives the filled containers after the containers have already been through a capping unit and received a cap. However, in this method the capping unit has not torqued down the cap, such that the headspace within the container is not sealed and is still in communication with the ambient environment through the gap that exists between the cap and the neck finish threads. The Pressure Sealing Unit subsequently seals the headspace from everything but the internal chamber of the sealing chamber, pressurizes the headspace within the sealing chamber and therefore the headspace within the container, and subsequently applies torque to the caps on the container in order to seal off the headspace with a raised pressure existing in the sealed container, which is then ejected from the pressure sealing unit. 
     With reference to  FIGS. 4   b - d,  the process within the sealing chamber for the method is shown whereby a typical cap applied by a standard capping unit but without having been forcibly torqued into position is shown on the container. The neck finish is enclosed within the chamber  84  of the pressure sealing unit. Following the introduction of fluid or gas or medium under pressure, the liquid or gas is forced into the container through the gap between the cap and the thread mechanisms of the neck finish, as shown by passage of liquid  86 . Once the desired pressure is obtained, the cap, as shown in  FIG. 4   c , can then be torqued into position by advancing the torque rod  85  within the chamber  84  while holding the container headspace at pressure. In this embodiment the method may be achieved using standard caps or modified caps as will be discussed next.  FIG. 4   d  illustrates removal of the torque rod  85 , correctly torqued cap  80 , immediately prior to ejecting the container head from the chamber  84 . 
     Typically in prior art, at a bottling plant, 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. 
     Figures onward from  FIG. 3   a  all refer to upper portions of containers as similarly shown in  FIG. 3   a.    
     According to a further part aspect of the present invention, and referring to  FIGS. 5   a - c,  following the introduction of a liquid, which may be already heated or suitable for subsequent heating, a cap may be applied including a small opening or aperture  81 . Thus a headspace  23   a  is contained under the main cap body  80  and above the fluid level  40  in the container. The headspace  23   a  is communicating with the outside air at this stage and is therefore at ambient pressure and allowing for the fluid level  40 . 
     As seen in  FIGS. 6   a - c,  in part of one embodiment, a sealing chamber  84  is applied over the neck finish and cap combination to seal the liquid from the outside air (the upper, closed end of the structure  84  is not shown). Following the introduction of a compressive force  50 , for example by way of injecting air or some other gas, the increased pressure within the sealing chamber provides for a subsequent increase in pressure within the headspace  23   b  and also forces the fluid level  40  to a lower point due to the subsequent expansion of the plastic container. 
     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. 
     As a further alternative, steam could also be injected into the headspace, providing for the increased pressure environment. 
     Now referring to  FIGS. 7   a - c  (the compressive force not shown), while pressure is maintained within the sealing chamber  84 , a plug mechanism  82  is moved downwardly from a delivery device  83  towards the aperture  81 . It will be appreciated the plug mechanism could be of many different styles. 
     As can be seen in  FIGS. 8   a - c,  while pressure is maintained within the sealing chamber  84 , the hole is closed off permanently by the placement of the plug  82  into the hole  81 . 
     At this point, and as can be seen in  FIGS. 9   a - c,  the headspace  23   b  is charged under a controlled pressure, dependant on the amount of gas delivered, and the sealing chamber may provide for withdrawal of the delivery device  83  following a release of pressure within the chamber as the container is ejected and returned to the filling line. 
     As shown in  FIGS. 10   a - c,  as the bottle subsequently travels down the filling line and is cooled, the headspace  23   b  expands as the liquid volume shrinks. The fluid level  40  lowers to a new position  41  and the pressurised headspace  23   b  expands and loses some or all of its pressure as it forms a new headspace  23   c.    
     Importantly, however, once the contents are cooled there is little or no residual vacuum in the container, or even perhaps a positive pressure. 
     As an alternative, and as shown in  FIGS. 10   d - f,  the plug  92  may be temporarily attached to the cap, for example by member  91 , during production of the cap. A liquid, as in the example illustrated, or steam or gas, could be injected in the same manner under pressure to circumnavigate the plug and enter the container headspace under pressure, and a rod mechanism  93  is then forced downwardly to advance the plug  92  into the hole permanently. In this alternative there is no need to load the rod with multiple plug mechanisms. 
     A further example of such an alternative is provided in  FIG. 18 . In this part embodiment of the invention the cap  80  has a plug  92  temporarily attached by a member (not shown). A sealing chamber  84  encloses the cap and provides an internal sealed chamber headspace  87  through the compression of sealing rings  89  against the upper surface of the cap. Gas or liquid, or a combination of both, is injected into the chamber headspace  87  through an inlet  86  and through the spaces around the plug into the headspace of the container. Once the required pressure within the container is obtained, the push rod  88  is advanced downwardly to force the plug  92  into position within the cap and therefore seal the container headspace under the required pressure. This provides for a calculated internal pressure to be achieved precisely at the time of sealing the container, when the plug is advanced into final position. This provides for forward compensation of the effects of subsequent vacuum generated by a cooling of any heated contents within the container. 
     With reference to  FIGS. 19   a  and  19   b , the present invention may be manufactured to function exclusive of cap application and for final sealing of any temporary cap hole or pathway only. A typical capping machine head unit  101  encapsulates the sealing chamber  84  and provides the function of sealing and pressurising the container through the cap to seal the container. A typical capping unit may have optionally already torqued the cap into position, but the container would remain unsealed due to the presence of a plug, being in an ‘unplugged’ position within the cap, and allowing the passage of liquid or gas between the inside and outside of the container. The precise moment of sealing the container occurs as the plug is rammed into position and the headspace within the cap is not at ambient pressure, as would be typical of prior art capping procedures within the filling and capping area, but instead, with the present invention, a headspace modification unit  102 , which may optionally be of typical rotary style in mechanics, may receive capped containers  1 , and subsequently pressurise the container immediately prior to sealing the container with a cap sealing plug. 
     It will be appreciated that the present invention offers multiple choices in carrying out a headspace modification procedure. 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. Various examples are disclosed in my further PCT specifications WO 2009/142510 and WO 2011/062512, both of which are incorporated in their entirety by reference. 
     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 part aspect of the present invention, summarized in  FIG. 17 , and referring to  FIGS. 11   a - c,  following the introduction of a liquid, which may be already heated or suitable for subsequent heating, a cap may be applied including a small opening or aperture  81  which is temporarily covered by a communicating seal  91 . Thus a headspace  23   d  is contained under the main cap body  80  and above the fluid level  40  in the container. The headspace  23   d  is not communicating with the outside air at this stage and is therefore at typical container pressure during the stages of cooling down on the filling line. 
     Alternatively, as seen in  FIGS. 11   d - f,  the opening may be temporarily covered by a liner seal contained within the underneath side of the cap and affixed to cover the hole. Construction of the cap would be virtually the same as any other cap containing an induction seal or internal liner, except the cap would contain a small hole that is non-communicating when the liner is in situ. 
     As seen in  FIGS. 12   a - c,  and again also referring inclusively to the example shown in  FIGS. 11   a - c,  once the container has been typically cooled to a level providing for labelling and distribution, the headspace  23   e  will be in an expanded state with a lowered fluid level, and will have created a vacuum due to the contraction of the heated liquid within the container. 
     As seen in this preferred part 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, or steam itself, or a mixture of steam and gas, the sterilising medium provides for the sterilisation of the internal surfaces of the sealing chamber  84  and the communicating seal  91 . 
     Now referring to  FIGS. 13   a - c,  while the sterilising medium is maintained within the sealing chamber  84 , a plug mechanism  82  is placed downwardly from a delivery device  83  towards the aperture  81 . The plug mechanism pierces the communicating seal  91  and is withdrawn again temporarily as shown in  FIGS. 14   a - c,  providing for communication between the sterilized volume within the sealing chamber above the cap  80  and the headspace  23   e  below the cap. The container pressure rises and so the fluid level  40  will drop unless replenished with liquid from the sealing chamber. 
     As can be seen in  FIGS. 14   a - c,  the sterilising medium, for example heated water at 95° C., is immediately drawn into the container through the open hole  81  due to the communicating seal being pierced. This causes equalization of pressure or removal of vacuum pressure within the container, such that the level of the headspace  23   f  rises higher. In another preferred embodiment the liquid would in fact be injected into the container under a small pressure supplied from the sealing chamber  84  such that the pressure within the container would in fact be a positive pressure and the headspace would in fact be very small. 
     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  FIGS. 15   a - c,  the delivery device  83  is advanced again such that the plug  82  will be injected into the hole to close it off permanently. At this point, the headspace  23   f  is under a controlled pressure dependent on the volume of liquid having been delivered to compensate for previous liquid contraction, as described above. 
     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 many forms of seal may be employed to provide 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  FIGS. 16   a - c,  the original headspace level  40 , experienced following cooling of heated contents within a closed container, provides for a vacuum to be present within the first headspace  23   d.  Following compensation, according this embodiment of the present invention, the headspace level changes and perhaps rises to level  41  depending on the pressure contained within the headspace, and the pressure within the headspace  23   f  is now preferably virtually at ambient pressure, or preferably slightly positive, such that the sidewalls of the container are supported by the slight internal pressure. 
     This particular part embodiment of the present invention is summarised in  FIG. 17 . 
     Referring to  FIG. 20 , a further part embodiment of the present invention is disclosed. The disclosed integrated system generally includes an empty container in-feed station prior to the filling station. This may be through pre-blown containers being fed into the Filling Enclosure, or may be through on-line blowmolding production as illustrated. In the case of on-line blowmolding, the preforms are fed into an integrated blowmolder that also has its own housing that may be continuously shielded alongside and joining the Filling and Capping Enclosures. 
     The system may also contain a continuous container conveying system, a container product fill station, a container head-space dosing station, an optional liquefied 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  FIG. 20 , the conveying system, fill station and container sealing station, or capping station, may all be integrally contained within an enclosure or integrated enclosures such that the inside environment may be pressurised. This will result in the headspace within each container being pressurised to the desired level as the capper seals the container. Effectively the ambient pressure within the enclosure is artificially elevated, while the container is sealed, and the internal pressure of the container rises immediately upon ejection of the filled and capped containers as they are presented to a lower ambient pressure outside of the system enclosures. 
     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  FIGS. 21   a - c,  an alternative embodiment of the present invention also incorporates at least one portion of the sidewall  801  configured to respond to vacuum pressure forces. In this particular embodiment, the amount of gas or liquid required to be forcibly injected into the container  1  within the sealing chamber  84  prior to sealing the cap  800  onto the container is reduced. 
     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  FIGS. 22   a - c  an alternative embodiment of the present invention also incorporates at least one transversely oriented pressure panel  802  in the container  1 . In this particular embodiment the transverse panel is located in the base portion of the container, but may equally be incorporated in the sidewall. In this particular embodiment, the amount of gas or liquid required to be forcibly injected into the container  1  within the sealing chamber  84  prior to sealing the cap  800  onto the container is also reduced. As explained above with reference to  FIGS. 21   a - c,  the transverse panel may account for a portion of the required vacuum compensation, for example 40%, when moved into the inverted position as shown in  FIG. 22   c  from the initial position as shown in  FIG. 22   a . Inversion of the element  802  may be by way of mechanical force for example. As the container can account easily for some of the vacuum compensation required, there is only a need to provide for approximately 60% of the required liquid contraction by way of pressure injecting prior to sealing the cap. In this way there is reduced stress applied to the container during processing. 
     With reference to  FIGS. 23   a - c  an alternative embodiment of the present invention provides for both sidewall vacuum compensation and transverse panel compensation to be combined with headspace compensation for even less stress to be applied to the container during processing. By way of example, it will be appreciated that if the sidewall compensation elements  801  provide approximately 30% of vacuum compensation, and the transverse panel  802  is able to provide approximately 40% of vacuum compensation, then a charge of gas or liquid into the headspace during sealing would only require approximately 30% of that required in a container not having vacuum compensation elements equivalent to  801  and  802 . It will be appreciated that varying amounts of compensation may be attributed to each element. 
     With reference to  FIGS. 24   a - c  a further alternative embodiment of the present invention is also provided. In the same way as already described, at least one portion of the sidewall may incorporate a vacuum compensation element  803 . In this particular embodiment, the element  803  is also configured to expand radially outwardly under internal pressure as illustrated in  FIG. 24   c . It will be appreciated that under internal pressure charge during headspace sealing the vacuum compensation element  803  will reduce the amount of stress within the container by expanding radially outwardly first. If filled with a heated liquid, the contents will subsequently cool inside the container and a pressure reduction will occur. As this happens the element  803  will return to the as moulded position shown in  FIG. 24   a  and will then subsequently be able to provide further vacuum compensation. By way of example only, if element  803  as shown in  FIG. 24   a  is able to provide approximately 30% of the required vacuum, then 70% of the compensation would be required to be introduced during headspace sealing. By incorporating a vacuum compensation element  803  that is able to expand outwardly then the stress induced is reduced during the initial phases by a significant amount. 
     With reference to  FIGS. 25   a - c  a further alternative embodiment of the present invention is also provided. It will be appreciated by the prior descriptions above that a container of the present invention may be provided with sidewall vacuum compensation elements or may be provided with sidewall vacuum compensation elements that are able to expand radially outward under pressure to reduce stresses during headspace modification and sealing procedures. These containers may also be provided with transverse pressure panel compensation elements also to further reduce the amount of stress required to be imposed on the container during processing. In this particular embodiment the transverse panel  802  is placed in the base of the container. It is envisaged by way of example and with reference to  FIGS. 24   a - c  and  FIGS. 25   a - c,  that element  803  may be able to provide approximately 30% of the required vacuum compensation and base element  802  may provide approximately 30% of the required vacuum compensation. Therefore, 40% of the compensation required would be injected into the headspace during processing as previously described. As sidewall element  803  is able to expand radially outward then the stress imposed during processing and headspace modification is reduced further. 
     With reference to  FIGS. 26   a - c,  even further stress reduction is anticipated in a further embodiment of the present invention. In a manner as described above, base element  804  is configured to expand longitudinally outward to relieve the pressure induced during headspace modification and injection of gas or liquid during sealing. This reduces the stresses imposed upon the container sidewall. In this particular embodiment, sidewall element  803  is also configured to expand radially outward under the internal pressure. Therefore substantial ability is provided within the container to reduce the stresses induced as gas or liquid is injected into the container. Upon subsequent cooling of any heated contents inside the container both sidewall element  803  and transverse element  804  are able to be inverted inwardly to assist vacuum pressure compensation. 
     With reference to  FIGS. 27   a   -d,  a further alternative embodiment of the present invention is provided. A rotary sealing unit  900  is disclosed that clamps the hot-filled container  1  by the neck finish and just under the neck support ring  33 . As the unit contains the upper neck thread of the container and prepares to increase the pressure contained in the pressure chamber  84  of the sealing unit, and the headspace of the container, the container is subjected to temperature modification. In this example a cold water spray  991 , typically below ambient temperature and preferably between approximately 4 degrees C. and 15 degrees C. 
     The cold water spray causes the container shell to immediately fall below the glass transition temperature of the sidewall material. The temperature within the container does not fall as rapidly however, and so the liquid contents are able to subsequently be used to sterilise the internal cap surface when the container is released from the Pressure Chamber and laid down in a horizontal position, typically for a period exceeding 30 seconds. 
     The container sidewalls are forcibly cooled until the central core temperature of the container falls below the glass transition temperature of the sidewalls. The cold spray of this example is maintained throughout the pressurisation and sealing period, beyond release from the unit and through the period immediately subsequent when the container is inverted, as is typical. The container liquid temperature will fall below the threshold value required soon after inversion has been completed. Once this has occurred the container may be returned to the production line without further cooling prior to entering the main cooling tunnels typically found some minutes down the production line. 
     As the container has now been ‘pre-chilled’ the efficiency of the main cooling process is improved also. 
     It will be appreciated that many cooling methods may be employed, for example a cold water bath  992  or the like, as illustrated in  FIGS. 28   a - d,  may be used instead of a spray. The cooling may be directed only at the base region or all over the container. A cooling jet of air may be used instead of a liquid for further example. Other cold gases may be used, eg nitrogen, or even ice may be used in some applications. 
     It will be appreciated that by preventing the material of the sidewalls of the container to be above a certain temperature, and below the temperature of the liquid contents for a critical period of time, then the pressure increase induced in the container will not cause damage to structures that would otherwise occur. 
     Preferably the cooling is applied for a period of time between 1 and 2 minutes, which time allows for the container to be pressurised, inverted to sterilise the cap underside with still-hot contents, and for the liquid to fall rapidly to below about 60 degrees C. 
     The time required will vary depending on line speed and fill temperature, however, and the cooling time required may be extended to over 2 to 4 minutes. 
     It is a preferred object of the present invention to provide a device which enables the pressurisation and sealing of freshly filled containers after sealing off the upper neck region of the container, and to initiate the differential cooling process to prevent the sidewall temperature exceeding approximately 70° C. and so avoid the deformation of container sidewalls that occurs through high thermal stresses and high pressure stresses. The process is summarized with reference to  FIG. 29 . 
     In a preferred embodiment of the present invention, the bottles must have a retained internal temperature above 80° C. for up to 30 seconds, and preferably up to 1 minute, more preferably up to 2 minutes, and occasionally even more preferably up to 3 minutes. During this time the temperature of the container body shell must be kept differentially below 70° C. and preferably below 60° C. for this time. During this period of time the containers may be inverted or laid horizontally to sterilize the inside underneath of the cap. 
     According to a preferred embodiment, the containers are rotated through an angle of between 70 degrees and 110 degrees, more preferably between 80 degrees and 95 degrees, so that they are transported approximately in a horizontal orientation. 
     The temperature of cooling medium and rate of application must be carefully controlled to provide only for the outside container surface to be held below 70° C., and so cause the internal container temperature to be maintained above 70° C., and more preferably above 80° C., and even more preferably above 90° C. 
     Of course it will be appreciated that if the glass transition point of an alternative sidewall material is above the fill temperature then applying a cooling period during sealing or inversion would not be required. 
     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 of the invention as defined in the appended claims.