SYSTEM AND METHOD FOR A STERILIZATION CHAMBER IN A FILLING MACHINE

Field of the Invention The present invention relates to a sterilization chamber in a filling machine for the production of liquid food packages, and more specifically to a system and a method for preventing blistering of packaging material in said sterilization chamber.

Background of the Invention

Filling machines having a heated sterilization chamber can get very hot during operation and during a stop, this heat is radiated off from the hot surfaces and is taken up by the packaging material . This can lead to blistering of the packaging material. Blistering is a phenomenon where the aluminium foil separates from the cardboard of the packaging material, such that blisters are formed. The blisters can in severe cases burst, and this leads to a problem with the aseptic property of the packaging material, as food product comes in contact with the blistered area. Normally, this necessitates disposal of a part of the packaging material . The packages can only be discarded when they have been filled, and it thus also leads to disposal of food product. This waste should be minimized.

Summary of the Invention

It is hence an object of the present invention to provide a system and a method for a sterilization chamber, which at least partly alleviates and mitigates the problems of the prior art. This is accomplished by providing a spray cooling system according to claim 1 in the sterilization chamber. Other embodiments are given in the dependent claims 2 to 11. A method for operating the system of claim 1 is given in claim 12, with other embodiments given in claims 13 to 16. A sterilization chamber having the spray cooling system of claim 1 is

disclosed in claim 17 and a filling machine comprising a spray cooling system is claimed in claim 18.

Brief Description of the Drawings

The invention will be described in more detail with reference to the appended schematic drawings, which show examples of presently non-limiting preferred embodiments of the invention, wherein

Fig. 1 is a side view in cross-section of a sterilization chamber in a filling machine according to the invention,

Fig. 2 is a front view in cross-section of the sterilization chamber in Fig. 1, and

Fig. 3 is a detailed view of a spray nozzle and its spray according to the invention,

Fig. 4 is an exploded view of an injector used for realizing the invention, Fig. 5 is a sectional view of an injector according to Fig. 4,

Fig. 6 is a second sectional view of the injector, as is used for realizing the invention, and

Fig. 7 is a schematical flowchart showing the air and liquid supply for operating the injectors in the system of the invention.

Detailed Description of the Invention

A system of the present invention is denoted 100 and can be seen in a filling machine in Fig. 1. The parts of the filling machine will only be explained briefly, and only in more detail if they interact with the system of the invention.

The system 100 is in Fig. 1 installed in a filling machine of the type having a heated sterilization chamber 10, where hydrogen peroxide that is used for sterilizing the packaging material is evaporated from a packaging material web 50, such that sterilisation can take place.

The packaging material web 50 is rolled off a big roll (not shown) and is on at least one side coated with hydrogen peroxide, in a way known per se. The coating of hydrogen peroxide can take place in a shallow or deep bath, through spraying onto the web, or by feeding the web past a roller that is coated with hydrogen peroxide, or in a similar way known to a person skilled in the art. The thus coated packaging material web 50 is then directed into the sterilization chamber 10, which is surrounded by a housing 11. The sterilization chamber 10 comprises rollers 12, 13 for guiding the web 50 back and forth in the chamber 10 in close proximity to at least one heating frame 14, see also Fig. 2. The heating frame 14 is supplied with several heating strips, which are indicated with 15 in Fig. 1, and these heating strips 15 are seen individually in Fig. 2. In Fig. 1, three substantially identical heating frames 14 are shown, but fewer or more frames 14 can be mounted, all having a plurality of heating strips 15.

At the back of the sterilization chamber 10, to the right in Fig. 1, a shield 16 is disposed, which is mounted on mounts 17 at a slight distance from the back wall of the housing 11 of the sterilization chamber 10. The shield prevents the housing 11 from becoming too hot.

When the packaging material web 50 leaves the sterilization chamber 10, it is guided by further rollers 21, 22 towards subsequent stations for the forming of a vertical tube, and filling, sealing and further treatment of filled packages in a way known per se.

The housing 11 is fitted with at least one injector 1, 2, which is mounted in a sidewall thereof, located to the right in Fig. 2. The injectors 1, 2 are mounted at a downward angle β of about 25 degrees relative to a horizontal plane. The injectors have a spray angle γ of about 60 degrees, which means that they cover an angle between 5 degrees upward to 55 degrees downward, see Fig. 3. The

spray is relatively thin in a direction perpendicular to the plane in Fig. 3, meaning that the injectors 1, 2 are producing a substantially sheet-shaped spray. It is, however, also possible to arrange the injectors 1, 2 to be substantially horizontal. This would then potentially require more injectors 1, 2 in order to cover the same surface area. The injectors can in alternative embodiments have different spray angles, such that they cover an intended area. Sprays with a slightly less sheet-shaped appearance are suitable when several hot items are to be covered, which are located a slight distance apart. In the shown embodiment, one injector 1 is placed at a higher level and towards the back of the sterilization chamber 10 (to the right in Fig. 1) . In this way, an upper part of the shield 16 can be affected by the spray from the injector 1, and the shield can be cooled down. The shield 16 is normally the hottest surface in the chamber 10. In one embodiment, the first injector 1 can be arranged to also hit the heating frame 14 closest to the shield 16, which frame normally represents the second hottest element in the chamber 10. The other injector 2 can be located at a lower level, and more to the middle of the sterilization chamber 10. In that case, the injector 2 will spray liquid onto the middle heating frame 14. It is obvious to a person skilled in the art that more injectors are possible, and that they can be ■ placed at different heights in the chamber 10, in accordance to the shown injectors in Figs. 1 and 2. Other injectors could e.g. spray liquid onto the remaining heating frames 14.

A temperature sensor 31 can in one embodiment be arranged to measure the temperature inside the sterilization chamber 10, see Fig. 1. This sensor can be connected to a control unit 30 via a line 34. Additional sensors are also possible, such as a concentration sensor 32,

which is coupled to the control unit 30 via a line 35, and a humidity sensor 33, which is coupled to the control unit 30 via a line 36. The output from the sensors is used as feedback for the control system, for controlling the duration and/or timing of the spray from the injectors 1, 2.

The injectors 1, 2 is in one embodiment supplied with pressurized air and a liquid with high heat of vaporization, such as water or hydrogen peroxide, and create a spray with an average droplet size of about 20 μm. The droplets from the injectors 1, 2 are preferably between 2 and 30 μm. Different injectors are possible, such as ultrasonic injectors or similar, and they do not have to be supplied with pressurized air. Suitable liquids are, as mentioned, hydrogen peroxide, water or a mixture thereof. A mixture of hydrogen peroxide and water would be sterile and would have a lower concentration than the pure hydrogen peroxide solution, which normally comprises about 35 % hydrogen peroxide. It would also be possible to use condensed water vapour from the filling machine, which is kept sterile and stored prior to being injected by the injectors 1, 2. Any sterile liquid with relatively high heat of vaporization can be used, as long as it complies with food safety regulations.

It would also be possible to produce the sterile liquid, e.g. water, in the filling machine. Suitable methods would be filtering, or treatment with UV radiation or exposure to gamma rays . Similar methods as are known to the skilled person are of course also possible.

In Fig. 4, one detailed example of an injector 1, 2 is shown in an exploded view, and in Fig. 5, the injector is shown in a sectional view. The injector comprises a base 101, which is mounted to the side of the sterilization chamber 10, and a house 102 for enclosing

the internal parts . A sealing 106 is placed between the base 101 and house 102 for enabling an air and water tight connection, and for thermally isolating the house 102 from the sterilization chamber 10. The injector further comprises, inside the base/housing assembly, an air cap 103, a nozzle 104 and a gasket 105. The air cap 103 is placed in a correspondingly shaped hole in the base 101, said hole being shaped to prevent rotation of the air cap 103, and the nozzle 104 is pressed against the air cap 103. The gasket 105 is placed on the outer part of the nozzle 104, and the house 102 is then mounted on the base 101 (with the sealing

106), keeping the air cap 103, nozzle 104 and gasket 105 in a press fit connection.

The house 102 is equipped with an air inlet 110 which leads to an annular channel 111, which is open to the left in Fig. 5. This channel 111 communicates, via holes in the gasket 105, with a corresponding ring-shaped channel 121 in the nozzle 104, in turn communicating with through-holes 121, substantially extending in the axial direction of the nozzle 104. The through-holes 121 of the nozzle open out into a space 130 between the air cap 103 and the nozzle 104. The pressure of the atomization air is about 1.5 bar gauge pressure.

The house 102 is further equipped with a liquid/steam inlet 113, for water, hydrogen peroxide, steam or similar. The liquid/steam inlet 113 communicates with an axially central bore 114 of the house 102, said central bore 114 in turn communicating with a central through-hole 123 of the nozzle 104, through the centre of the gasket 105. The central through-hole 123 leads to a cone-shaped transition into a small pipe 133 fitted in a centrally located aperture in the air cap 103. The axially central bore 114 is also connected to a drain

hole 112, for leading away liquid and/or steam inside the injector. The fluid connection flowchart is shown in Fig. 7 for a case where four injectors 1, 2 are mounted in the sterilization chamber 10, two on either side of the sterilization chamber 10. The injectors are supplied with sterile water through a first pipe 200, and sterile air through a second pipe 210. The flows of sterile water and air are mixed at the outlet of the injector 1, 2, where the air is directed towards the central water jet at an almost 45 degree angle. This creates a highly atomized water flow, resulting in a very small droplet size, as is indicated in Fig. 6. The injectors 1, 2 are activated by an air supply (not shown) , through line 230, which activates an actuator 140 that lifts a needle 141, both shown schematically in Fig. 5.

The heat exchanger 202 is supplied with water by closing valve 206 and opening valve 205, which is connected to a fresh water supply (not shown) . Excess water is drained off into a funnel 207 connected to a drain (not shown) . The heat exchanger 202 is emptied by closing valve 205 and opening valve 206. This is normally done at the end of production of the filling machine, such that the injectors 1, 2 can be sterilized directly at the beginning of the next production.

During sterilisation of the injectors 1, 2, high temperature steam is supplied from the inlet 201 and through the first pipe 200 to the injectors 1, 2. The pressure of the steam is about 1.7 bar gauge pressure, and its temperature is about 130 ⁰ C. The heat exchanger 202 is empty, thus not affecting the steam to the injectors. The steam comes in contact with the interior of the injectors, and kills all potential bacteria. All condensation during the sterilisation process is drained through the drain hole 112, leading to the drain pipe 220. The drained water is discharged through a steam trap

221, which lets liquid out while retaining the steam. A vacuum breaker 223 is fitted in communication with the steam trap 221, for avoiding damage to the steam trap caused by a low pressure that can occur when a drain valve 222 is closed and steam condenses between the valve 222 and the steam trap 221. Thermometers (indicated in Fig. 7) can optionally be arranged near the injectors, in order to monitor that the steam is sufficiently hot for sterilization purposes.

When the sterilisation by steam is finished, the heat exchanger 202 is filled with water, and the steam in the heat exchanger immediately condensates and flows towards the now closed drain valve 222. Due to the condensation of the steam in the pipe 200, the pressure is reduced and more steam is drawn into the heat exchanger until the first pipe 200 is filled with water up to the water level of the heat exchanger 202. The system is now ready to be activated, for spray cooling of the sterilization chamber 10 during any stops.

When the filling machine has to be stopped, the air for activating the injectors and the sterile air for the atomization are almost simultaneously activated. The water flow is driven by the steam pressure at the inlet 201, and more water is continuously condensed as water is consumed .

The water is in one embodiment pulsed in short bursts, injecting during one second and then pausing for one second. During the pause, the atomizing air is normally not turned off, since this has been shown to improve the atomization consistency during a subsequent injection pulse. When a filling machine is in steady-state operation for the production of aseptic packages, the packaging material 50, carrying a thin film of hydrogen peroxide, is heated up to about 85 ³ C. The heat makes the hydrogen

peroxide on the packaging material evaporate, and it also activates the killing mechanism of the hydrogen peroxide. Due to the constant heating with the use of the heating strips 15, all surfaces of the sterilization chamber 10 are hot, e.g. the shield 16, the heating frames 15 and the heating strips 14. At more or less regular intervals, the machine may need to be stopped in order to correct an error, or to adjust a setting, and the feeding of the packaging material is then interrupted. The hot parts of the filling machine 14, 15, 16 can then transfer heat to the packaging material, such that blistering can occur. In order to avoid blistering, the spray nozzles 1, 2 are used for spraying a liquid towards the hot internal parts, such as the shield 16, and the heating frames 14 with the heating strips 15, in order to cool down the hot parts and reduce the heat transfer to the packaging material web 50.

The liquid in the form of a mist sticks to the internal surfaces of the sterilization chamber 10, and is evaporated, and this cools down the hot surfaces . In this way, blistering can be avoided. The duration of the spraying is preferably between 10 and 50 seconds. The duration of the spraying depends on the temperature of the sterilization chamber 10.

In one embodiment, this temperature is measured by the temperature sensor 31, and is used for controlling the duration of the spraying such that only the necessary amount of spray is injected. This temperature depends on various factors, such as web width, time since start-up etc. The temperature signal is sent via line 34 to the control unit 30, which in turn controls the injectors 1, 2. The control unit 30 can be the standard control system of the filling machine, or be a separate system. It is also possible to use output from other sensors, such as the concentration sensor 32 and/or the humidity sensor

33, as input for controlling the spray from the injectors 1, 2. The concentration sensor 32 can be used if hydrogen peroxide solution is used as the sprayed liquid, and the humidity sensor 33 can be used if sterile water is used as the sprayed liquid. The duration and/or the timing of the spray can then be controlled by the control unit 30, in response to the measured data from the sensors 31, 32 and 33.

In Fig. 2, an embodiment is shown in which a condenser 5 is used for condensing steam, indicated with A. The condensed steam will by definition become sterile water, and this is lead via B to a storage tank 6. Lines 3 and 4 are provided for leading the sterile water to the injectors 1, 2. A pump (not shown) is used for providing an adequate water pressure for achieving the desired spray behaviour, with regard to water flow, droplet size, spray pattern etc .

In one embodiment, which is only shown schematically in Fig. 7, four injectors are mounted in the sterilization chamber 10, where two injectors are mounted on either side of the sterilization chamber 10. In this way, the injectors spray liquid from both sides, for a faster cooling of the hot parts in the sterilization chamber.