The present invention relates to a system for treating packaging containers, and in particular to such a system used in a filling machine. The invention also relates to a corresponding method. Background

In filling machines, where a liquid or semi-liquid product is filled into a packaging container asepticity is an issue. It is crucial that the packaging container is sterilized and that the sterilized properties are maintained, at least until the packaging container has been sealed. The context to which this particular application relates is a filling machine for ready-to-fill (or RTF) packaging containers, which are filled through an open end thereof. In order to maintain sterile conditions in a filling machine for such packaging containers, one could consider creating a homogenous uni-directional flow of sterile air, preventing impurities to enter through the open end of a packaging container. This may be accomplished by having perforated plates in the top of the filling machine, through which plate sterile air may flow in a controlled fashion.

The present applicant has however, in a copending application, presented an alternative inventive solution where an aseptic zone is generated by the use of jets. This technique is described referring to Figs. 2 and 3, and is not considered to be comprised in the state of the art at the time of filing of this application. When introducing jet flows in an atmosphere through nozzles the phenomenon of entrainment occurs, implying that the jet flow having a large velocity will entrain air from its surroundings. In a filling machine where packaging containers are sterilized, filled and sealed, use of jets may be beneficial since jets are efficient in breaking boundary layers so as to provide good contact between the contents of the jet, and the packaging container to be treated. However, in such filling machines it is also crucial that an aseptic zone is established and maintained, and in this context the use of a jet may induce problems related to uncontrolled entrainment of surrounding air, and disturbance of other, uni-directional flows in the filling machine. Some aspects of this are also disclosed in WO2007/024172 and -173, as well as references cited therein. It should be noted that the problem of entrainment may also occur as liquid is filled into the packaging container, which liquid flow may also entrain contaminants, pointing out the issue of entrainment is not relevant for high- velocity flows only. In the above mentioned applications a partial solution to the entrainment problem, which will be further elucidated in the detailed description, is provided by creation of an injection nozzle which feeds itself with entrainment air, at least in a steady state situation.

The general solution to the above problem is otherwise to provide external air to be entrained, such that the quality of the entrained air may be controlled, and in view of prior art it may be straightforward for the skilled person to provide

entrainment air through a perforated plate arranged on an upstream side of the nozzle even if such a solution is not known to the applicant. This possibly would provide a flow of air of controllable quality surrounding the jet flows, thus providing air for entrainment. Depending on the field of application there may be advantages yet also several drawbacks with the use of a system comprising perforated plates for this purpose. Firstly, the system will be space consuming, since the flow of the air on the upstream side of the perforated plate has to be controlled too. One example is that the perforated plate is arranged in one partition of a large manifold, in which an overpressure is established, forcing air through the perforated plate. This approach is obviously space consuming. Secondly, for food applications a perforated plate may be unsuitable from a hygienic standpoint, since it offers a large surface per volume for contaminants to settle on. To that end a perforated plate may also be difficult to clean, in particular in an automated fashion while it is positioned in a machine.

Summary

The present invention provides a solution eliminating these and other drawbacks in prior art, by providing a system for treating packaging containers, comprising a channel having an upper section and a lower section, transportation means adapted to transport the packaging containers through the channel with an open end located in the upper section, nozzles in the upper section of the channel for introducing jets in the direction of the transportation means for treatment of the packaging containers, and means for evacuating air in the lower section of the channel, wherein the system comprises means for providing a flow of sterile-entrainment air in a longitudinal direction of the channel in a portion of the upper section of the channel, such that air to be entrained in the jet flows may be provided by the sterile air.

The provision of a feed flow of filtered, sterile air to the jets will prevent the jet from entraining air from its surroundings in an uncontrolled manner. If such a feed was not present the surrounding air entrained instead would generate a reduced pressure, and the risk of air flowing from the lower section of the channel would be ever present. In a situation where the upper section is considered aseptic and the lower section is not, the result would be devastating since it would ruin the aseptic properties of the upper section. The present invention provides a solution to this problem. If too much sterile, filtered air is provided it may be considered a waste, yet since the evacuation means are in the lower section of the channel it will only result in a stronger general flow in the direction from the upper section to the lower section and thus not compromise the aseptic properties of the upper section, which is considered the paramount feature. The sterile filtered air used is suggestively HEPA-filtered sterile air. Further, if no entrainment air is provided the jet injected through the nozzle will be quenched, resulting in a less divergent jet, which also may flicker and be prone to be drawn towards walls and such in an unstable manner.

According to one or more embodiments the flow of sterile air is a free flow, directly or indirectly guided by the channel, not requiring the use of conduits inside or outside of the channel. To arrange conduits inside the channel results in a more complicated geometry, which may disturb the flow field and render cleaning of the channel more difficult. Using a free flow without constraints is also a cost efficient solution.

In one or several embodiments the nozzles are adapted to generate

recirculation zones when a jet is injected, and wherein the flow of sterile entrainment air is arranged to be lead through the recirculation zone. The recirculation zones will have a center with lower pressure than the surroundings, and therefore they may be used to guide the flow through the upper section of the channel. In one or more embodiments the channel may have a longitudinal waist with a cross sectional dimension smaller than areas above and below the longitudinal waist. The waist will simplify the maintenance of an upper aseptic section, and also simplify the generation of stable recirculation zones and guidance of the entrainment air flow.

The inventive system may in one or several embodiments provide entrainment air for jets injected by nozzles arranged in a series along the length of the channel. In this way a single feeding system may be utilized for several nozzles, eliminating the need for individually tailored solutions. The nozzles may according to one or more embodiments be arranged along, or symmetrically along, a center longitudinal line of the channel, and the flow is arranged to be guided between said series of nozzles and the longitudinal side walls of the channel on both sides thereof.

The present also relates to a method for using said inventive system, i.e. in a filling machine, a method of supplying entrainment air to jets injected by nozzles arranged in an upper part of a channel through which packaging containers having an open end turned upwards are transported in a machine direction, comprising the step of:

guiding a free flow of entrainment air in a longitudinal direction in an upper section of the channel. The channel may have a longitudinal waist having a cross sectional dimension smaller than areas above and below the longitudinal waist and the flow of entrainment air may in one or more embodiments be guided in an area above said waste.

In accordance with the inventive system the flow may be guided in and along the approximate center of these recirculation zones.

Brief Description of the Drawings

Fig. 1 is a partial, schematic overview of a filling machine utilizing the inventive system and method according to one embodiment of the present invention.

Fig. 2 is a partial cross section of one zone of the above filling machine, according to one embodiment of the present invention.

Fig. 3 is a cross section similar to Fig. 2, of another embodiment of the present invention. Description of Embodiments

Fig. 1 is a schematic partial overview of a filling machine in which the inventive system is used. Packaging containers 108 having an open bottom end 110 turned upwards are transported on transportation means 114 in a transportation direction from right to left in Fig. 1. The channel 100 in which the packaging containers 108 are transported may be a channel 100 having an essentially uniform cross section, or a cross section having a defined waist, which is illustrated in Figs. 2 and 3, respectively, yet other cross sections are also possible. Before entering the view of Fig. 1 the packaging containers 108 have passed a preheating zone and a sterilization zone, and in the latter they have been subjected to a sterilization agent. After the sterilization zone a gas lock is arranged such as to eliminate flows from left to right in this section. In the venting zone (V) it is secured that no significant residuals of sterilization agent remain in the packaging containers. The injection nozzles used for this purpose may be of the type disclosed in the previously mentioned applications. In the subsequent filling zone (F) the packaging containers are filled with their contents, such as milk or fruit juice, etc. After leaving the view of Fig. 1 the open end 110 of the packaging containers 108 is sealed and folded in a suitable configuration. After this point the packaging containers 108 may again be subjected to non-aseptic conditions.

HEPA-filtered sterile air is forced into the system via a vertical channel, and is used to maintain asepticity in adequate zones of the filling machine, provide sterile air to be injected, and to provide entrainment air for injected jets, the latter of which will be described in more detail. The sterile air that may be provided to the injection nozzles, for pre-heating, sterilization and ventilation may be distributed via a manifold (not shown) arranged on top of the channel in which the packaging containers are lead.

Returning to the channel 100, no matter the cross section, the channel is operably divided into an upper section or upper volume and a lower section of lower volume. The upper volume is defined by its aseptic conditions and has means for injecting gas, generally sterile filtered air, in some of its sections. In the filling zone, nozzles arranged in the upper volume are used in order to create a barrier between the upper volume and the lower volume. This is described referring to Fig. 2 and 3, and is further described in a copending application filed by the same applicant, on the same day, and it will thus not be described in detail here. However, in short the function is as follows:

Fig. 2 illustrates one embodiment of the invention, and represents a schematic cross section, orthogonal to the transportation direction of the packages (the machine direction MD), in the filling zone of the filling machine. The package 108 is carried by a carrier 114 attached to a transportation line 115. Two rows of gas injection means in the form of circular nozzles 116 are arranged in the top of the zone, and these inject sterile air downwards. The injected air from each nozzle 116 forms a diverging flow, as indicated by the dotted lines extending from the nozzle opening, on its way downwards. From a fluid mechanics standpoint the flow is turbulent and it will not be described in detail here. In one practical example an exit velocity may be in the region of 10-20 m/s, e.g. 13 m/s, and the nozzle-hole diameter 4 mm, i.e. in the turbulent region or transitional region. The dash-dotted line indicates the approximate position of an interface area between the first volume, above the line, and the second volume, below the line. In the same examples the nozzles 116 are arranged in two rows, with about 20 mm center-to-center distance of adjacent nozzles 116. In the interface area, there will always be a unidirectional flow, efficiently forming a gas flow barrier preventing mass transport from the second volume to the first. The aseptic or sterile first volume may thus remain aseptic or sterile, independently of the atmosphere in the second volume. The level of the interface area (in the up-down direction in Fig. 2) may vary depending on if a package 108 is present or not, as well as during transportation of the package 108, but it must be stressed that the flow in the interface area will remain continuous at all times, which results in that a fixed and reliable level may be established above which the sterile or aseptic conditions are maintained, in the atmosphere as well as on surfaces of the machine and the package. The nozzles 116 may be arranged in rows, generally in pairs of nozzles 116 so as to define a symmetric setup. In the drawings there is one set of nozzles for each package indexing position, yet in the present working apparatus the nozzles 116 are arranged with a smaller distance in between, such that more than one pair of nozzles 116, on an average, is arranged in each indexing position. Since the generated flow is of relatively high velocity it will not as easily affected by interfering flows as prior art techniques. E.g. when this concept is used in the filling zone of a filling machine, the interfering flows generated by the flow of a product into the package 108 will not affect the continuity gas flow barrier in the interface region. Interfering flows from neighboring zones, such as from the venting zone, will not affect the maintenance of the gas flow barrier. Gas evacuation means 122 are arranged in the second volume.

In the venting zone injection nozzles similar to those presented in

WO2007/024172 and -173, may be used.

In order not to jeopardize the integrity of the gas flow barrier entrainment air should be provided to the injected air flows, in the venting zone as well as in the filling zone. If no additional air is provided there is a risk that an injected air flow will entrain surrounding air in an uncontrolled manner and, in a worst case, generates a flow traversing the gas flow barrier and compromises the aseptic properties of the upper volume. In order to avoid this additional air may be provided. The

straightforward manner to accomplish this would be to add perforated plates in the ceiling of the upper volume, as has been mentioned before. This, however, is an expensive and relatively complicated solution requiring relatively large mass flows. The inventive way of solving this is to generate an essentially horizontal flow of sterile filtered entrainment air along the length of the channel, as illustrated by the symbols 124. This steady and adjustable flow of air may provide a reliable source of entrainment air, and in combination with the overall flow direction having a component directed downwards, the integrity of the gas flow barrier will not be jeopardized. The essentially horizontal flow of entrainment air along the channel will be tapped off as it is entrained into the jets, and will thus have a downwardly directed component.

Fig. 3 illustrates another embodiment. In this embodiment flow restrictors 118, 120 have been arranged in the channel. In this way the void volume around a package 108 is reduced. This makes it possible to use less diverging injections of air through the nozzles 116, and easier to obtain a gas barrier, when a package 108 is present, when no package 116 is present, as well as during transportation of packages 108. The divergence of the nozzles 116 may be varied by varying their geometry, in a known manner. The flow restrictors will generate stabilized recirculation zones on the outside of the rows of nozzles 108 (in relation to an imaginary centerline between the nozzles), which is indicated by the curved, dotted arrows. This design of the channel will also increase the volume (which may be seen in Fig. 3) available for the entrainment flows.

In this case also, the essentially horizontal flow along the length direction of the channel is illustrated by the symbols 124 and will essentially propagate along the length of the channel, which combined with the recirculation flows will generate a swirling flow of entrainment air propagating in a direction generally opposite the machine direction MD. As air is entrained this swirling flow will be weaker and as the flow reaches a gas lock effectively separating the sterilization zone from the venting zone the horizontal component is essentially eliminated, since the path of least resistance will be downwards.

It is important to note that the essentially horizontal flow is a free flow, not bound by a conduit or line, which would complicate the flow pattern and the construction, in turn making the ever so important asepticity more difficult to maintain. The control of the flow is essentially conducted by controlling the air injected through the nozzles in the venting and filling zone on the one hand, and the air evacuated from the gas evacuation means arranged in the second volume. With the proper balance the flow of sterile HEPA air will enter into the upper channel automatically. To further facilitate this flow path a blockage means, e.g. in the form of a plate 132 covering a major part of the cross section of the lower volume of the channel 100 at the downstream end of the filling zone. A similar blockage may be arranged in the interface between the sterilization zone and the venting zone at the upstream end, to obstruct gas exchange there between, and at this end the blockage may be arranged to cover essentially the entire cross section, while only leaving an opening allowing the packages to be transported in the machine direction.

The gas evacuation means may be provided as conduits 122 extending in the cross direction of the channel 100, at a distance corresponding to the distance between carriers 114. Apart from their main task, the conduits will then also serve the purpose of stabilizing the channel 100. The conduits may have an evacuation nozzle, e.g. in the form of a circular opening, at a bottom side thereof. If all evacuation conduits 122 are combined with the same evacuation manifold the control of evacuation rate for each evacuation nozzle may be arranged by adjusting the cross section of each nozzle. The overall evacuation rate may then be controlled by a main evacuation means, e.g. by an evacuation pump connected to the manifold. Each nozzle may have a variable cross section, yet according to one or more preferred embodiments the cross section is optimized and fixed (though not necessarily the same for each nozzle). The gas evacuation means will thus serve the dual purpose of supporting the ever so important vertical flow in the channel as well as supporting the horizontal flow in the channel.

To briefly return to the view of Fig. 1, the flow of entrainment air will propagate through the length of the illustrated channel, and on its way portions of it will be drawn to the lower volume. It will continue to propagate along the channel until it reaches said gas lock, preventing it from entering the sterilization zone. The origin of the HEPA filtered sterile air is the flow entering from the HEPA channel 130. This has the dual purpose of feeding the flows of entrainment air and to maintain the asepticity in the aseptic zone of the filling machine, by generating flows directed from the aseptic zone towards non-aseptic zones.

The term "sterile air", "air flow" and so forth have been used throughout this application. The skilled person realizes that is locations of the filling machine residues of e.g. sterilization agent will be present in the atmosphere, and that the presence of such residues should not affect the scope of protection as defined by the claims.

The present invention may be applied in a filling or packaging machine, further details of which are described in a number of copending Swedish patent applications, filed by the same applicant on the same day as the present application, which hereby are incorporated by reference. To this end further details of:

A nozzle that may be used when treating the interior of the packaging containers is disclosed in the application with the title "A device and a method for gaseous-treatment of packages" (SE-0900911-9).

A method for obtaining an optimized concentration of sterilization agent in a sterilization zone is disclosed in the application with the title "A device and a method for sterilizing packages" (SE-09009077).

A device and method for maintaining asepticity is disclosed in "A device and a method for maintaining a gas flow barrier between two interconnected volumes" (SE- 0900911-9), of which an alternative device and method is disclosed in "A device and a method for maintaining a gas flow barrier between two volumes of a channel" (SE- 0900913-5)

A device for providing cleaned air, which may be used for the as a source of entrainment air and surplus air in the filling zone for the present invention, is disclosed in the application with the title "A device for cleaned air provision" (SE- 0900908-5).

Some various aspect of the filling or packaging machine are disclosed in the applications titled "Packaging machine and packaging method I" (SE-0900909-3) and "Packaging machine and packaging method II" (SE-0900910-1), respectively. A system for supplying entrainment air to jet air flows in the machine are disclosed in the application with the title "A system for treating packaging containers" (SE- 0900912-7), relevant parts of which, as mentioned, are hereby incorporated by reference.