SE462281B - Method and device for continuous sterilization of packaging containers by means of steam and microwaves - Google Patents

Abstract

Method and device for a two-stage sterilization procedure comprising supply of water vapour to, and microwave treatment of, packaging containers or parts thereof. In a pressurized housing 10 there are two areas, a first one 21 and a second one 22, for applying a microwave field to the containers. The containers 11 are heated to a temperature of about 80 degree as they are conveyed through a feed sluice 12 to the treatment zone, and the saturated steam from the valve 23 is pulsed by means of a valve that can be opened and closed, for example a valve of the magneto-restrictive type. To optimize the delivery of the microwave energy to the condensed, thin layer of water on the surfaces of the packaging containers, a reflector 28 is arranged around the area 22. The amount of steam in the chamber or zone 10 is kept essentially constant by means of a steam trap 32 at the lower end of the zone, by dimensioning the trap with respect to the steam delivered from the steam generator. The outlet from the housing or the zone 10 is provided with a rotating sluice or revolver magazine of the same type as the inlet. A given overpressure is maintained at the outlet from the sluice 35. This prevents re- contamination from the environment before the packaging containers have been filled in a filler 40, which follows directly on a protective casing 39 adjoining the outlet sluice 35. In order, where necessary, to complement the steam with further sterilization medium, there is also a hydrogen peroxide line 42 which supplies hydrogen peroxide in mist form via a valve 43 and at a temperature of about 60 - 80 degree C. The final temperature which is obtained in the microwave area 22 is such that the hydrogen peroxide is heated to a temperature well in excess of 100 degree C, which means that the elimination of microorganisms is extremely good, while at the same time the hydrogen peroxide breaks down and leaves a very small amount of residues. <IMAGE>

Description

462 281 z a wide frequency range and with overpressure. The reason for the improved heat transfer is that the pulsation gives a movement of the steam, so that the heat supply is not diffusion-limited. This reduces the risk that the condensate will form a heat transfer barrier for bacteria on the surface of the packaging containers or the parts of such containers.

In one embodiment of the invention, the pulsation takes place with a magneto-strictive high-pressure valve, which can quickly pulsate the steam supply. Possible pressure variations are 3.0 - 3.5 bar and ditto frequencies are 1 Hz - 50 KHZ.

This improved heat transfer with pulsed steam supply is especially advantageous when the packaging containers have a large mass.

When the steam hits such a package, it is condensed but, depending on said large mass, the condensate is also cooled comparatively fast, meaning that the surface without the special pulsation of the steam according to the invention does not reach the desired high temperature necessary for sterilization of surface. A high surface temperature, in the range 120 - 160 ° C, is very important for safe sterilization of commonly occurring packaging materials.

In addition to pulsing the steam flow, an additional interesting possibility is also proposed to improve the killing. Thus, it is proposed to use hydrogen peroxide, if necessary, as a complement to the meadow microwave sterilization.

In order to enable the process involved in the further development of the invention, a device is also provided, in which the invention in particular provides a new type of successively pressure-changeable feed chamber to the pressurized, closed environment in which the sterilization process takes place. The input arrangement resp. discharge ditto also provides an effective microorganism barrier to the treatment zone. More structured, the invention provides a method of sterilizing packaging containers or parts thereof.

The method is characterized in that containers are supplied to a pressurized zone, that the containers are fed from an entrance to an outlet in said zone, that the containers are applied water vapor in a first area of the zone, and that the containers thereon, in a second area following the first in the feed direction a microwave field.

In a preferred embodiment, the water vapor is applied as pulsed, saturated water vapor. The steam can suitably be given a temperature in the range of about 120 - 145 ° C, and the containers are preferably preheated to a temperature in the range of about 80 - 90 ° C before entering the first area.

The pulsation can be done within a wide frequency range, preferably 1 Hz - 50 KHz.

In order to make the most efficient use of the microwave field's energy-emitting capacity, taking into account that the microwave effect needs a certain penetration depth for transfer to the water - half the microwave effect in the present case is absorbed by a water depth of about 6 mm - a microwave reflector so that it encloses individual packages in said second area of the zone.

In a further embodiment of the invention, the containers or container parts are also supplied with hydrogen peroxide mist in the first area.

The invention also provides a device for sterilizing packaging containers or parts thereof. The device is characterized by an elongate housing defining a first area for processing packaging containers in a first step and a second area for microwave processing of the packaging containers, by an entrance in the housing to the first area of said zone, by an exit in the housing from the other area of the zone, and by means for transporting the containers between the entrance and the exit.

In the preferred embodiment, a steam generator is arranged to deliver saturated water vapor to the first area.

Preferably, there is a valve device which has means for periodic opening and closing of the valve, the steam generator being connectable to said valve.

In a further developed version of the device, there is also a device arranged to emit a mist of hydrogen peroxide to the first area.

In a preferred embodiment, the entrance to the first area of the pressure zone is designed as a revolving type revolving magazine with magazine pockets adapted to the packaging container dimension, and a pump device is arranged to successively lower the pressure in each magazine pocket as the pocket rotates towards the first area.

In order to be able to optimally utilize the microwave effect, a microwave-reflecting jacket is preferably arranged in the second area and encloses one or more containers.

In order to achieve a comparatively stable and constant steam flow in the housing, there is suitably a steam trap arranged in the housing, in the feed direction seen after the second area, and the cooling jacket is dimensioned to condense a quantity of steam substantially corresponding to that supplied by the steam generator.

In one embodiment, the outlet also comprises a magazine of the rotating type and of the same type as the input magazine, and also here a pump device is arranged to lower the pressure in each magazine pocket as such approaches the container discharge position.

In a suitable embodiment, the pump device is arranged to have produced a certain overpressure in the discharge position of the discharge pocket, and this overpressure is maintained by a substantially closed casing which extends to a filler.

In a simple embodiment, said means for transporting or feeding containers comprise a housing inclined relative to the horizontal plane, the cross section of which allows transport of the containers while transmitting the force of gravity.

In one embodiment, the steam generator and the possible hydrogen peroxide misting device are dimensioned to give an overpressure of the order of 0.5 - 6 atö in the housing.

For the sake of completeness, it should also be emphasized that microorganisms or bacteria present on the packaging material through their water content contribute to the heating, when the microwave field is applied. The microwave field thus does not only work against the thin water layer. It can also be expressed in such a way that bacteria are thereby killed, or for a contribution to their death, through the microwave supply.

An embodiment of the invention will now be described with reference to the accompanying schematic figure.

Reference numeral 10 denotes an elongate, pressure-resistant housing serving as the treatment zone where the packaging containers or parts thereof undergo the sterilization process. Such a container has been schematically shown with the reference numeral 11. It may, for example, be a bottom-sealed, can-like package, a can lid, trough or the like In order to be able to maintain said high pressure inside the housing 10 there is at the upper end in the figure a feed lock 12. This is designed as a revolver-type magazine device rotatable about a shaft 13. The dashed lines 14 indicate individual magazine pockets, and with the opening 15 the feeding point for individual packages or containers 11 is shown.

The walls 16, 17 which on either side terminate the turret magazine may be made of some friction-lowering material, for example Teflon. In order to now gradually lower the pressure in each magazine pocket 14, there is a pump arrangement consisting of an ejector pump 18 and a rotary pump 19. The former is able to go continuously against atmospheric pressure, while the final pressure reduction is effected by means of the rotary pump 19 In practice, this means that each magazine pocket 14 has a state of vacuum when the pocket comes in a position in the middle of an inlet opening 20 to a first area 21 of the pressure zone in the chamber 13.

Since the volume of each individual magazine pocket is small compared to the internal volume of the housing 13, the pockets do not significantly contribute to pressure pulsation in the housing. On the other hand, it helps to effectively remove microorganisms present in the surrounding air.

A line 22 from a steam generator (not shown) opens into the first region 21 of the housing 13. The line terminates with a valve 23, which in the present case is a magnet-strictive high-pressure valve, which is controlled by an oscillator 24 and a control unit 25. The steam from the steam generator is preferably saturated water vapor of a temperature of around 120 - 145 ° C. The reason why the steam supply is pulsed has previously been clarified, and it can be stated that as the package or packaging part 11 approaches the next treatment area, the second area, in the zone formed by the housing 13, is located on the surface of the container, inside as well as externally, a thin layer of water, which maintains a temperature determined by the cooling mass of the container and the heat transfer steam-condensate.

In order to now give this container the final "push", in order to achieve a high surface temperature (around 145 ° C), a microwave generator, magnetron 26, is used, which transmits the energy via waveguide 27 to the container or containers 11 in the area 22. .

In order to make this energy transfer optimal, a reflector 28 is arranged around the area 2 and thus around the thin water layers having the containers 11. The microwave radiation thus has an opportunity to repeatedly pass through the thin water layers and thereby emit most of its energy. To absorb non-transmitted energy, there is an absorber 29 at the end of the waveguide 27. End walls 30, 31, for example of ceramic or polyethylene terephthalate "Teflon" delimit the microwave area from other parts of the treatment zone. The walls have suitable passages for the containers. The microwave energy - in combination with the steam heating that takes place in the area 21 - thus causes heating to the high surface temperature. In order to maintain a well-defined steam environment in the area 21 as well as the area 22, there is a steam trap 32 at the exit from the area 22, consisting of a return line 33 to the steam generator and a cooling water loop 34 around the housing 10. The condensation is set so that the flow of steam in through the valve 23 corresponds to the amount of water required for generation in the steam generator for the steam stream just mentioned.

At the outlet of the housing 10, at its lower end in the figure, there is a rotating magazine device 35, also of the revolver type and of the same type as the magazine 17. The overpressure in individual magazine pockets 14 'is taken care of by a pressure reducing valve 36.

The pressure from the outlet 37 from the area 22 to the outlet 38 from the turret magazine 35 is suitably reduced to such an extent that a certain overpressure is present in a discharge housing 39 from the turret magazine 35. This pressure, for example of the order of 0.2 - 0.4 atm, prevents ambient air from entering the packaging containers or packaging parts before they reach a filler 40. This filler 40 may be of the turret type and rotate about an axis 41, so that individual pockets for receiving containers 11, successively appear at the exit of the housing 39. .

In order to supplement or further improve the killing if necessary, according to the invention an additional generator, a hydrogen peroxide generator in vapor form, can be used. A pressure line 42 from a hydrogen peroxide source (not shown) is connected to a valve device 43, for example of the same type as the valve 23, and is controlled by a control unit 44. The control is such that the valve 43 is opened and closed at a certain frequency, e.g. 1 Hz - 50 KHz.

Suitably there are also means (not shown) for preheating the hydrogen peroxide to a suitable temperature, eg around 80 ° C.

The combination of water vapor from valve 23 and hydrogen peroxide from valve 43 is adjusted in the most suitable manner, taking advantage of the superior killing properties of hydrogen peroxide by raising the temperature in area 22 to a level well above 100 ° C.

At the same time, the hydrogen peroxide will decompose at this high temperature, leaving very low residues. Although a specific embodiment of the invention has been described, it will be understood that modifications and alternatives are possible within the scope of the appended claims.

Claims (15)

462 281 PATENT REQUIREMENTS 1. A method for sterilizing packaging containers or parts thereof during continuous feeding thereof through a sterilization chamber, characterized in that containers are supplied to a pressurized zone, that the containers are fed from an inlet to an outlet in said zone, that the containers are applied to water vapor. in a first area of the zone, that the containers thereon, in a second area following the first in the feeding direction, a microwave field is applied, and that a microwave reflecting jacket (28) is arranged to enclose packaging containers in said second area of the zone. 2. A method according to claim 1, characterized in that the water vapor is supplied as pulsed, saturated water vapor. 3. A method according to claim 2, characterized in that the water vapor is given a temperature in the range of about 120 - 140 ° C, and that the containers are preheated to a temperature in the range of about 80 - 90 ° C before entering said first area. 4. A method according to claim 3, characterized in that the pulsation is performed at a frequency in the range 1 Hz - 50 KHz. A method according to claim 1, characterized in that the containers are also applied to hydrogen peroxide mist in the first area of 2011911. Apparatus by the method of claim 1 for sterilizing packaging containers or parts thereof during continuous feeding through a sterilization chamber, characterized by an elongate housing (13) defining a first area (21) for treating packaging containers (11) with water vapor in a first stage and a second region (22) for microwave treatment of the packaging containers in a second stage, of an entrance (12) in the housing to the first region, of an outlet (35) in the housing from the second region, and by means for transporting the containers between the inlet and the outlet. Device according to claim 6, characterized in that a steam generator is arranged to deliver saturated water vapor to the first area (21). Device according to claim 7, characterized in that a valve device (23) has means (24, 25) for periodic opening and closing of the valve, and that the steam generator is connected to said valve device. Device according to claim 8, characterized in that means (42-44) are arranged to emit a mist of hydrogen peroxide to the first area. Device according to claim 6, characterized in that the entrance to the first area is designed as a rotatable magazine of the turret type with magazine pockets (14) adapted to the packaging container dimension, and that a pump device (18, 19) is arranged to successively lower the pressure in each magazine pocket (14) as the pocket rotates toward the first area (21). 11. ll. Device according to claim 6, characterized in that a microwave-reflecting jacket (28) is arranged in the second area of the zone and encloses one or more containers. Device according to claims 10 and 11, characterized in that a steam trap (32) is arranged in the housing, in the feed direction seen after the second area (22), and that the cooling jacket is dimensioned to condense a quantity of steam corresponding to that supplied by the steam generator. Device according to claim 12, characterized in that the outlet comprises a magazine (35) of the same type as the input, and that a pump device (36) is arranged to lower the pressure in each magazine pocket as it approaches a container discharge position. . Device according to claim 13, characterized in that the pump device is arranged to give a certain overpressure in the discharge position of the discharge pocket, and that this overpressure is maintained by a substantially closed housing (39) up to a filler (40). Device according to one or more of the preceding claims, characterized in that the steam generator and the possibly present hydrogen peroxide generating device are dimensioned to give an overpressure of the order of 0.5 - 6 atö in the housing.