Abstract:
A method for sterilizing packaging material comprises an emitter that is adapted to emit charge carriers, in particular electrons, wherein the charge carriers form at least one cloud, and wherein the emitter and the packaging material are moved relative to each other so that a flow of a gaseous medium is established in between the emitter and the packaging material. The method comprises the steps of: controlling a movement profile between the emitter and the packaging material; sterilizing the flow of the medium in between the emitter and the packaging material by adjusting the movement profile so that the flow of the medium in between the emitter and the packaging material is sterilized. Also disclosed is a device for sterilizing packaging material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/901,349 filed on Dec. 28, 2015, which is a U.S. National Stage application based on International Patent Application No. PCT/EP2014/062960 filed on Jun. 19, 2014, which claims priority to Swedish Application No. 1350773-6 filed on Jun. 25, 2013 and Swedish Application No. 1450100-1 filed on Jan. 31, 2014, the entire content of all four of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a method for sterilizing packaging material and to a device for sterilizing packaging material. 
       BACKGROUND DISCUSSION 
       [0003]    In the prior art different devices and methods for sterilizing packaging materials are known. One method widely used in the prior art is sterilization by means of gases and in particular by means of hydrogen peroxide. However, efforts are being made to reduce the use of chemicals when sterilizing containers. Therefore, devices and methods have also become known which sterilize material by means of ultraviolet radiation or electron beams. In general for electron beams, there is provided an emitter that is adapted to emit charge carriers, in particular electrons, wherein the packaging material can be sterilized by these charge carriers. For this purpose the packaging material and the emitter, respectively, are moved relative to each other, e.g. an electron gun is put into a bottle-shaped package. However, when the emitter and the packaging material are moved relative to each other, flows or streams of a medium, such as air, are established in between. If these streams or flows comprise a medium, such as air, that is not sterile or aseptic, there exists the risk that parts of the packaging material that have already been sterilized are re-infected by the unsterile or non-aseptic air-streams or—flows. 
       SUMMARY 
       [0004]    Therefore, it is an object of the current invention to provide a method for sterilizing packaging material and a device for sterilizing packaging material to maintain aseptic conditions on a packaging material during and after the sterilization. 
         [0005]    This object is achieved by a method for sterilizing packaging material according to claim  1  and by means of a device according to claim  13 . Additional advantages and features of the embodiments of the current invention are defined in the dependent claims. 
         [0006]    According to the invention, the method for sterilizing packaging material comprises an emitter that is adapted to emit charge carriers, in particular electrons, wherein the charge carriers form at least one cloud, and wherein the emitter and the packaging material are moved relative to each other so that a flow of a gaseous medium is established in between the emitter and the packaging material, the method further comprises the steps of:
       controlling a movement profile between the emitter and the packaging material;   sterilizing, by the at least one cloud, the flow of the gaseous medium in between the emitter and the packaging material by adjusting the movement profile.       
 
         [0009]    Actually, the flow of the medium in between the emitter and the packaging material is usually established in a gap that is established in between the emitter and the packaging material. The gap can have a constant size or thickness, when the packaging material is for example flat. However, the gap does not have to be constant, its size can change, respectively, when the emitter and the packaging material are moved relative to each other. This means that the gap can get thicker and/or thinner when the emitter and the packaging material are moved relative to each other. The speed of the flow of the gaseous medium in the gap depends on the size/thickness of the gap and the speed of the relative movement. The speed of the medium is the faster the smaller the gap is and/or the quicker the relative movement is. The object of the invention is to sterilise the flow of the gaseous medium in the gap by the cloud of electrons from the emitter. 
         [0010]    However, if the speed of the flow of the gaseous medium in the gap is too fast, the time is too short to sterilize the medium. This means that the medium that has passed the cloud is not sterilized. According to the invention, the flow of the medium in between the packaging material and the emitter is controlled by adjusting the movement profile. In other words, the flow of the medium is controlled in a way so that the flow of the medium in between the emitter and the packaging material is sterilized. Especially, the speed of the medium in the gap is controlled via the movement profile. The speed of the medium should be slow enough to allow sterilization time when it passes the electron cloud. The speed of the medium depends on the size of the gap and the movement profile in between the emitter and the packaging material or on a relative speed in between the emitter and the packaging material, respectively. The smaller the relative speed between the emitter and the packaging material is, the smaller is the speed of the flow of the medium. 
         [0011]    The movement profile is adapted to control the speed of the flow of the medium in the gap so that sterilization of the flow of the medium can be realized. For this purpose, the cloud of electrons is adapted to cover preferably the complete gap. This ensures that the entire flow of the medium that passes the gap is sterilized, i.e. that all the medium flowing in through the gap is sterilized. The cloud forms an aseptic barrier when the emitter is extracted. The present method makes it possible to maintain aseptic conditions in the packaging material during and after the sterilization. In other words, it can be made sure that any gaseous medium that comes into contact with the (sterilized) packaging material is sterile. 
         [0012]    The movement profile can be adapted to every gap size. This means that the packaging material can have any form or geometry. According to the “medium” it has to be mentioned that the medium is not specifically constrained concerning its mixture. It may be for example air or nitrogen or any other gas or mix of gases. “Medium” means a medium that is may not be sterile. In general a medium is meant something that could re-infect the already sterilized packaging material. Sterilization is a term referring to any process that eliminates or kills microbial life, including transmissible agents such as for example fungi, bacteria, viruses and spores, which may be present on a surface of the packaging material or in a product. In the (food) packaging industry this is generally referred to as aseptic packaging, i.e. packaging sterilized products in sterilized packaging containers, i.e. keeping both the product and the packaging container free form living germs and microorganisms, so that the freshness of the product can be preserved without special cooling requirements, i.e. so that sterility can be maintained inside a packaging container although it is stored in ambient temperature. In this context the term “commercially sterile” is also commonly used and means in general the absence of microorganisms capable of growing in the food at normal non-refrigerated conditions at which the food is likely to be held during manufacture, distribution and storage. In this patent application the word “sterile” refers to a condition being at least commercially sterile. 
         [0013]    In one or more embodiments the packaging material is basically tube-shaped, and the emitter is adapted for sterilization of at least the interior of the tube-shaped packaging material through an opening of the tube-shaped packaging material. 
         [0014]    The opening is adapted to enable an insertion of the emitter into the basically tube-shaped packaging material. The basically tube-shaped packaging material is closed at its other end portion opposite the opening. The tube-shaped packaging material extends along an axis. The term “tube shaped” comprises no limitations concerning the possible form of the cross-section of the basically tube shaped packaging material. This means that the cross section can be round, rectangular, circular, polygonal and/or angular and especially, the cross section of the basically tube shaped packaging material does not have to be constant along the axis. Without limiting the generality the basically tube-shaped packaging material is sometimes named “packaging container” in the following. 
         [0015]    The packaging container can for example be made of a plastic material such as for instance PET, or be made of a (laminated) carton material. With regard to the later a common type of laminated carton material is the ones comprising a core layer of paper or paperboard and one or more barrier layers of, for example, polymer material or aluminium foil. An increasingly common packaging type is the “carton bottle” manufactured in a filling machine in that packaging blanks of the above-described packaging laminate are formed and sealed as a sleeve. Said sleeve is closed in one end in that a top of thermoplastic material is injection moulded directly on the sleeve end portion. The sheets of packaging laminate may be cut from a magazine reel of packaging laminate. 
         [0016]    Advantageously, the opening of the packaging container, e.g. the spout or a bottom of the packaging container, has to be big enough so that at least the portion of the emitter comprising the electron exit window can be passed through it, to sterilize in particular the interior surface of the packaging container. In one or more embodiments the emitter has a round, in particular a circular cross section that is basically constant. A diameter of the cross-section lies within a range of about 5-100 mm. 
         [0017]    In one or more embodiments the method comprises the step of:
       performing a mutual relative movement between the emitter and the tube-shaped packaging material, during which movement a portion of the emitter is temporarily inserted through the opening of the tube-shaped packaging material, such that interior sterilization of the packaging material takes place.       
 
         [0019]    The term “relative movement between the emitter and the tube-shaped packaging material” comprises every possible movement arrangement. In one or more embodiments the emitter moves in relation to the packaging container (the packaging container being stationary along the axis). Alternatively, in one or more embodiments the packaging container moves towards and away from the emitter (the emitter being stationary along the axis). The emitter will hence be inserted into the packaging container in that the emitter is received in the packaging container. In other words, the packaging container will be moved to surround the emitter. Alternatively, in one or more embodiments, both the emitter and the packaging container are moved. Each performs a part of the relative movement. 
         [0020]    Inserting the emitter into the basically tube-shaped packaging material creates basically an outflow of the medium out of the basically tube-shaped packaging material through the opening wherein pulling the emitter out of the basically tube-shaped packaging material creates basically an inflow of the medium into the basically tube-shaped packaging material. The method comprises the step of:
       adapting an inflow-speed and an outflow-speed of the medium using the movement profile.       
 
         [0022]    For the sake of completeness, to avoid ambiguity, it is to be understood that the term “inserting” and pulling out” refers to a relative movement. Hence, “inserting” includes any movement of the emitter and the packaging container towards each other. Correspondingly, the term “pulling out” includes any movement of the emitter and the packaging container away from each other. 
         [0023]    Pulling the emitter out of the basically tube-shaped packaging material creates basically an inflow of the medium into the basically tube-shaped packaging material. The method comprises the step of:
       adapting an inflow-speed of the medium, using the movement profile, such that the inflow of the medium into the basically tube-shaped packaging material is sterilized by the cloud. In other words, the medium flowing into the packaging container is sterilized by the cloud.       
 
         [0025]    The aforementioned inflow is created in the same way when the emitter does not move and the packaging material is moved away from the emitter. In the same way, the outflow is created when the emitter does not move and the packaging container is moved towards (and pulled over) the emitter. In one or more embodiments the inflow-speed as well as the outflow-speed of the medium can be decelerated by decelerating the relative movement speed between the emitter and the packaging material. In one or more embodiments, the side of the packaging container opposite the opening (through which the emitter is inserted) is preferably closed. This means that the medium or the air, respectively, that is inside the packaging container, when the emitter is inserted into the container is pushed out of the container creating the outflow of the medium. Similar to this, air or medium, respectively, around the packaging container is sucked into the packaging container via the opening or the gap, respectively, when the emitter is pulled out from the packaging container. This means that un-purified, non-aseptic or non-sterile medium/air could come into the container if the flow of the medium via the gap is not sterilized by the cloud. However, advantageously the movement profile is adapted in a way so that the flow of the medium that comes into the packaging container is slow enough so it can be sterilized by the emitter while passing the cloud of the emitter. 
         [0026]    In one or more embodiments the movement profile comprises at least a first position, wherein at the first position the emitter, in particular its electron exit window, and the opening of the basically tube shaped packaging material are basically on the same level, and a second position, wherein at the second position the emitter, in particular its electron exit window, is located inside the basically tube shaped packaging material, the method comprises the step of:
       adjusting the movement profile so that a time span for moving from the first position to the second position, defined as run-in, is shorter than a time span for moving from the second position to the first position, defined as run-out.       
 
         [0028]    Naturally, in for example a filling machine, there is only a certain span of time available for the sterilization of the inner part of the packaging container. In one or more embodiments a plurality of emitters are provided on a carousel or the like which is adapted to rotate (the basic arrangement is known from the prior art). Expediently, the packaging containers which are transported for example via a conveyor reach the carousel and are attached to one of the (rotating) emitters. During at least a part of one rotation of the carousel, the sterilization takes place and the packaging container is removed from the appropriate emitter or from the carousel, respectively. Therefore, dependent on the size of the carousel, the number of the emitters arranged at the carousel and/or the rotation speed of the carousel a certain span of time for sterilization is available. If having a non-sterile emitter and if the carousel is arranged in a non-aseptic chamber, the sterilization is preferably made during the run-out of the packaging container. The cloud will itself form an aseptic barrier in the packaging container. During run-in the emitter will be in operation, however the actual sterilization will start when the cloud fills the closed end of the packaging container, i.e. when the cloud is positioned farthest away from the opening. As the emitter is pulled out of the packaging container the aseptic barrier is moved upwards, towards the opening. 
         [0029]    To allow for sufficient time for run-out, to control the speed of the in-flow, the time for run-in is adjusted to be shorter than the time span for run-out. If the time span for run-out is longer, the available time span for sterilization the inside of the packaging material during run-out is longer and the inflow can be adjusted so that it can be sterilized by the cloud, i.e. such that any medium flowing in can be sterilized. 
         [0030]    Making the time span for run-out as long as possible, the medium flowing in via the gap can be sterilized by the cloud because it is as slow as possible. It goes without saying that the run-out does not stop at the first position. The opening of the packaging container is only a reference point that was chosen to describe the movement profile. The second position is preferably a deepest position of the emitter, in particular its electron exit window, inside the packaging container. Of course, the second position is located preferably so deep inside the packaging container that the cloud can reach the whole inside of the side of the packaging container, which is opposite to the entry side, i.e. the opening. As a consequence, the second position depends on the length of the packaging material or container and on the size of the cloud. In one embodiment, a distance between the first and the second position measures about 10 and 400 mm. The available time span for sterilization, in other words the time span for run-in and run-out measures about 0.1-10 s in total. 
         [0031]    In one or more embodiments the method comprises the steps of:
       adjusting the time for run-out to be at least 5-times as long as the time for run-in;   sterilizing the basically tube-shaped packaging material during run-out.       
 
         [0034]    In one or more embodiments the time for run-out is at least 8-times as long as the time for run-in, especially preferred the time for run-out is at least 10-times as long as the time for run-in. As a consequence, the time for sterilizing the packaging material during run-out can be increased. 
         [0035]    The tube-shaped packaging material extends basically along an axis, the cloud comprises a width that extends basically perpendicular to the axis, and the cloud comprises a length that extends basically along the axis. In one or more embodiments the method comprises the steps of:
       providing a power supply, wherein the power supply is adapted to influence the width and the length of the cloud;   forming the width so that it is adapted to cover at least the area between the emitter and the packaging material.       
 
         [0038]    This means that the cloud is adapted to cover preferably the entire gap. Also preferably, the cloud or the width of the cloud, respectively, is also adapted to cover the diameter of the opening. Generally, the gap measures about 1 to 50 mm. Obviously, the emitter diameter should be less than the diameter of the packaging container, to provide for a gap, and thereby easy movement of the emitter and the packaging material relative to each other. Expediently, the place in between the emitter and the surrounding packaging material or the gap, respectively, is covered completely by the cloud. In other words, the gap is completely closed by the cloud so that the entire medium that passes the gap has to pass the cloud. As a consequence, it can be easily reacted on different gap sizes by adjusting the width of the cloud. In combination with controlling the movement profile between the packaging material/container and the emitter it can be ensured that the inflow of non-sterile/non-aseptic air/medium, i.e. the medium flowing in, is always sterilized, independent of the form of the packaging material. In addition, the power supply is adapted to control that the inside of the packaging container is not overexposed to the electrons, i.e. that the output dose rate of the emitter is not too high. 
         [0039]    In one or more embodiments, the method comprises the step of:
       adapting the energy level of the charge carriers and/or the dose rate of the emitter as a function of the flow-speed of the medium in between the emitter and the packaging material.       
 
         [0041]    In particular, the energy level of the charge carriers and/or the output dose rate of the emitter, respectively, is adapted as a function of the inflow-speed of the medium in between the emitter and the packaging material, at least during run-out. 
         [0042]    The idea is to align the energy level of the charge carriers and/or the output dose rate, respectively, to the speed of the medium, in particular the speed of the inflow of the medium. This means, the energy level of the charge carriers and/or the output dose rate, respectively, should be the higher, the higher the flow-speed, in particular the inflow-speed is. This can ensure sufficient sterilization of the inflow. In one or more embodiments the energy level of the charge carriers and/or the output dose rate of the emitter, respectively, are not constant during the entire movement profile. Expediently, the energy level is increased during run-out to ensure sterilization of the inflow of the medium, i.e. sterilization of the medium flowing in. It goes without saying that adjusting the energy level of the electrons and/or the output dose rate of the emitter is preferably combined with adjusting the movement profile itself. 
         [0043]    In one or more embodiments the method comprises the step of:
       adapting the length and/or the width of the cloud during run-out when the emitter is outside the packaging material to cover the opening of the packaging material with the cloud.       
 
         [0045]    The speed of the medium or the gas, such as air, respectively, depends not only on the size of the gap when the emitter is positioned within the packaging material. There is also an inflow of the medium when the emitter is already outside the packaging material. This is based on the inertia of the flow of the medium. In other words, the inflow after pulling the emitter out of the packaging container still exists when the emitter is already above the aforementioned first position. This means that the speed of the inflow of the medium depends also on the speed of the emitter when leaving the packaging material. In one or more embodiments, the length and/or the width of the cloud are increased when the emitter is outside the packaging material during run-out, in other words, when the emitter is slightly above the opening of the packaging container (first position). Preferably, the cloud is adapted so that the inflow is sterilized by the cloud. The cloud should have a width w larger than the opening of the packaging container to ensure sterility of the inflow. 
         [0046]    In one or more embodiments the method comprises the steps of:
       lowering and/or stopping the run-out speed when the emitter is above the opening;   adapting the cloud being big enough to cover at least temporarily the opening;   sterilizing the inflow of the medium.       
 
         [0050]    This means that the movement profile in between the packaging container and the emitter is preferably adjusted so that the relative speed between the packaging material and the emitter is lower, decreased or stopped, respectively, when the emitter is above the opening. This makes sure that an inflow that is sucked into the packaging container after the emitter has been pulled out of the container is also sterilized. 
         [0051]    In one or more embodiments the method comprises the step of:
       providing a drive unit to enable the movement profile by moving the packaging material along the axis.       
 
         [0053]    In one or more embodiments the drive unit comprises any of the following: a linear motor, a servo motor, a pneumatic drive/motor or a mechanical drive such as for example a cam curve. Alternatively, also a standard (rotating) electric motor can be used, wherein a mechanism is provided that translates the rotation in a stroke move. In one or more embodiments a linear motor is used. The linear motor has a minimum stroke that enables the aforementioned distances between the first and the second position and even longer distances (as in the first position the emitter is only on the level of the opening of the packaging container). 
         [0054]    In one or more embodiments the method comprises the step of:
       pre-loading a drive mechanism of the linear motor using a pre-load device to improve a speed of the motor.       
 
         [0056]    As already mentioned, it is preferred to shorten the time for run-in. As a consequence, for moving the packaging container or the emitter, a motor has to be provided that is very strong to enable the appropriate accelerations. To enable the usage of smaller and as a consequence also cheaper electric motors the drive mechanism of the electric motor can be combined with a pre-load device as for example a spring or a rubber element that can be used to support the movement of the drive mechanism or the electric motor, respectively. In other words, the pre-load device can be compresses or the like and the stored energy can be used to support the possible accelerations of the electric motor. 
         [0057]    In one or more embodiments the method comprises the steps of:
       creating overpressure inside the basically tube-shaped packaging material to prevent the inflow coming into the basically tube-shaped packaging material.       
 
         [0059]    In one or more embodiments the emitter comprises at least one outlet or the like to create a condition inside the packaging container that prevents medium from outside from coming into the container. A pressure inside the container is bigger than a pressure outside the container. It could be also possible to generate an outflow of e. g. sterile air out of the container that stops the inflow that exists during pull-out of the emitter. 
         [0060]    According to the invention, there is also provided a device for sterilizing packaging material, comprising an emitter that is adapted to emit charge carriers, in particular electrons, wherein the charge carriers form at least one cloud, and wherein the emitter and the packaging material are moved relative to each other so that a flow of a gaseous medium is established in between the emitter and the packaging material, wherein the devise comprises a control unit that is adapted to control a movement profile in between the emitter and the packaging material, wherein the flow of the medium in between the emitter and the packaging material can be sterilized by adjusting the movement profile. 
         [0061]    The device according to the invention can include the features and advantages of the methods according to the invention and vice versa. 
         [0062]    Additional advantages and features of the current invention are shown in the following description of embodiments of the current invention with reference to the attached drawings. Single features or characteristics of respective embodiments are explicitly allowed to be combined within the scope of the current invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0063]      FIG. 1 : shows schematically a flow of a medium between an emitter and a packaging material that move relative to each other; 
           [0064]      FIG. 2 a   : shows schematically an outflow of a medium when an emitter is inserted into a basically tube-shaped packaging material; 
           [0065]      FIG. 2 b   : shows schematically an alternative packaging container and an emitter; 
           [0066]      FIG. 3 : shows schematically an inflow of a medium into a basically tube-shaped packaging material when an emitter is pulled out of the basically tube-shaped packaging material; 
           [0067]      FIG. 4 : shows two movement profiles; 
           [0068]      FIG. 5 : shows schematically how an inflow can be sterilized by a cloud of an emitter; 
           [0069]      FIG. 6 : shows a sterilization of an inflow of a medium when an emitter is already pulled out of a basically tube-shaped packaging material; 
           [0070]      FIG. 7 : shows an adaption of a cloud to sterilize an inflow into a basically tube-shaped packaging material. 
       
    
    
     DETAILED DESCRIPTION 
       [0071]    Referring now to  FIG. 1 , a packaging material  10  is shown that is moved along a direction of an arrow a. An emitter  20  is positioned so that a gap  14  is formed between the emitter  20  and the packaging material  10 , wherein the emitter  20  comprises an electron exit window  24 . The electron exit window  24  faces down towards the packaging material. The gap  14  is covered by a cloud  22  that is formed by charge carriers, in particular electrons, that are emitted by the emitter. The movement of the packaging material  10  relative to the emitter  20 , which does not move, establishes a flow  42  of a medium in between the emitter  20  and the packaging material  10  or in between the emitter  20  and the packaging material  10 , respectively. As  FIG. 1  shows, the direction of the flow  42  of the medium is directed basically opposite the arrow a. The relative movement in between the emitter  20  and the packaging material  10  or a movement profile, respectively, is adapted or adjusted so that the flow  42  of the medium in between the emitter  20  and the packaging material  10  is sufficiently sterilized by the cloud  22 . 
         [0072]      FIG. 2 a    shows an embodiment of an emitter  20  that is inserted into a basically tube-shaped packaging material  10 . In particular, the basically tube-shaped packaging material  10  is a packaging container in a shape ready to be filled with product through an opening  12 . It comprises a sleeve body  10   a  and a top portion  10   b . The top portion  10   b  comprises a neck or spout sealed with a closure. The closure can for example be a screw cap, flip-cap (hinged cap) or membrane. The sleeve body  10   a  is provided with the opening  12 . 
         [0073]    In this embodiment the opening  12  of the packaging container  10  is an open bottom end, which after filling will be sealed and folded to form a substantially flat bottom surface. It should however be understood that this opening  12 , through which the emitter  20  is received and through which filling will be made, may in other embodiments be arranged in the top portion  10   b  of the packaging container, as a neck or spout portion of the packaging container  10 .  FIG. 2 b    illustrates such embodiment. The neck or spout portion will, after filling, be sealed by for instance a screw cap. 
         [0074]    In  FIG. 2 a    it is seen that the packaging container extends along an axis A. The emitter  20 , which also extends along the axis A, is inserted into the packaging container  10  along an arrow a. In between the packaging container  10  and the emitter  20  a gap  14  is formed. The emitter  20  comprises an exit window  24  that is adapted to emit charge carriers, in particular electrons. During inserting the emitter  20  into the packaging container  10  an outflow  44  of a medium inside the packaging container  10  is established in the gap  14  wherein the outflow  44  exits the inside of the packaging container  10  via the opening  12 . 
         [0075]    In the following an exemplary emitter  20  for sterilizing the interior of this ready-to-fill packaging container  10  will be briefly described. 
         [0076]    The emitter  20  comprises an electron generator for emitting a substantially circular electron beam along a path. The electron generator  14  is enclosed in a hermetically sealed vacuum chamber. Said vacuum chamber is provided with an electron exit window  24 . 
         [0077]    The electron generator comprises a cathode housing and a filament. In use, an electron beam is generated by heating the filament. When an electrical current is fed through the filament, the electrical resistance of the filament causes the filament to be heated to a temperature in the order of 2000° C. This heating causes the filament to emit a cloud of electrons. The electrons are accelerated towards the electron exit window  24  by means of a high-voltage potential between the cathode housing and the exit window (being the anode). Subsequently, the electrons pass through the electron exit window  24  and continue towards the target area, i.e. in this case the interior surface of the packaging container  10 . 
         [0078]    The filament can be made of tungsten. A grid may optionally be placed between the filament and an electron beam exit window. The grid may be used for diffusing the electron beam into a more uniform beam, and for focusing the electron beam towards the target area. 
         [0079]    The high-voltage potential is created by for example connecting the cathode housing and the filament to a power supply and by connecting the vacuum chamber to ground. The emitter  20  is generally denoted low voltage electron beam emitter if the voltage is below 300 kV. In one or more embodiments the accelerating voltage is in the order of 90-110 kV. In one or more embodiments the voltage is 100 kV. This voltage results in a kinetic (motive) energy of 100 keV in respect of each electron. However, another voltage can be chosen, for example in the interval 75-150 kV. 
         [0080]    The emitter  20  is, as mentioned, further provided with an electron exit window  24 . The window  24  can be made of a metallic foil, such as for example titanium, and can have a thickness in the order of 4-12 μm. A supporting net (not shown) formed of aluminum or copper supports the foil from inside the vacuum chamber. The electrons are exiting the vacuum chamber through the exit window  24 . 
         [0081]    The vacuum chamber may, as shown in for example  FIG. 2 b    or  5 , be made up of two elongate cylindrical bodies  20   a ,  20   b  with substantially circular cross sections. The cylindrical bodies have a common longitudinal centre axis A. The first cylindrical body  20   a  has an end surface, in a plane being perpendicular to the centre axis A, being provided with the electron exit window  24 . The electron exit window  24  is circular and preferably extends over most of the end surface. The diameter of said first body  20   a  is small enough to be inserted into the ready-to-fill packaging container  10 , the cross section of said first body is dimensioned such that it can be guided through the opening  26  of the packaging container  10 . The second body  20   b  is provided with the electron beam generator, and the diameter of said second body  20   b  is larger than the first body  20   a.    
         [0082]    The emitter  20  emits, from its electron exit window  24 , an electron cloud  22  illustrated schematically by a line in for example  FIG. 5 . The cross sectional shape is somewhat circular, as shown, or droplet-shaped. The shape of the electron cloud is defined by the shape of the electron exit window  24  and by the Brownian motion of individual electrons leaving the electron exit window. When leaving the electron exit window and enter into air the electrons will scatter in all directions forming a cloud. The cloud formed is basically axis-symmetrical, around axis A, and the cloud volume is thereby spherical (or droplet-shaped). To obtain sterilization of the interior surface of the packaging container the energy of the emitter  20  needs to be matched with the sterilization time available, the packaging container size and shape and the packaging container velocity relative the emitter. 
         [0083]      FIG. 3  shows basically the same embodiment as  FIG. 4 . However, the emitter  20  is pulled out of the packaging container  10  along the arrow a. This establishes an inflow  43  that is directed into the packaging container  10  via the opening  12  and the gap  14  which is established in between the packaging container  10  and the emitter  20 . It goes without saying that this effect is the same when the packaging container  10  is moved against the arrow a and the emitter  20  is stationary, i.e. when the emitter does not move along the arrow a (that applies also to the movement in  FIG. 2 a   ). 
         [0084]    As previously mentioned the emitter and the tube-shaped packaging container are adapted to perform a relative movement. Although the emitter is in operation (emitting a cloud) during the entire relative movement, the actual sterilization of the interior of the tube-shaped packaging material is considered to be made when the emitter is pulled out of the tube-shaped packaging material. In such case the emitter itself does not need to be sterile and the cloud forms an aseptic barrier between the sterilized interior surface and the emitter. Such aseptic barrier can be maintained as long as the inflow  43  of gaseous medium can be controlled such that it is secured that it is sterilized by the cloud. In other words, any inflow  43  of gaseous medium should be sterilized in the cloud before being able to cross the aseptic barrier and reach inside the sterilized tube-shaped packaging material. This will be further described in relation to  FIGS. 4 and 5 . 
         [0085]      FIG. 4  shows two movement profiles  90 ′ and  90 ″ in a diagram. The x-axis x of the diagram shows the time, e. g. in ms. The y-axis y shows a lift or a distance, e. g. in mm, respectively. The lift refers to a first and a second position, wherein at the first position an emitter  10 , in particular its electron exit window  24 , and an opening  12  of the packaging container  10  are basically on the same level, and wherein at the second position the emitter  20 , in particular its electron exit window  24 , is located inside the packaging container, as for example shown in  FIG. 2 a   . The second position is adjusted so that the entire inside of the packaging container  10  can be sterilized by the cloud  22  of electrons. This means that the second position has to be so deep inside the packaging container  10  so that the cloud can reach the inside of the packaging container  10  sufficiently. The movement profile  90 ′ shows a time span for run-in  91  that is much shorter than a time span for run-out  92 . In one or more embodiments the time span for run-in  92  measures about 150 ms, wherein the time span for run-out  92  measures about 1350 ms. Contrary to this, the movement profile  90 ″ shows that a time span for run-in  91  is basically as long as a time span for run-out  92 . 
         [0086]    In the case of non-sterile emitters, the movement profile  90 ′ is the preferred one. The emitter may then enter the tube-shaped packaging container quickly causing a quick outflow  44  ( FIG. 2 a   ). Alternatively, the tube-shaped packaging material is quickly raised to surround the emitter. Sterilization of the interior surface of the tube-shaped packaging material “starts” when the cloud fills the top portion  10   b  of the tube-shaped packaging material. The emitter can then be slowly retracted from the packaging material, or alternatively, the packaging material can be slowly moved away from the emitter. The cloud will form an aseptic barrier that, during the relative movement, will be displaced towards the opening  12  in the tube-shaped packaging material, leaving a sterile interior surface in the packaging material underneath the cloud. The relative slow motion will prevent the inflow  43  of gaseous medium to flow through the cloud without being sterilized. This is further described in  FIG. 5 . 
         [0087]      FIG. 5  shows an embodiment for sterilizing an inflow  43  that is directed into a basically tube-shaped packaging material  10  which extends basically along an axis A by a cloud  22 . An emitter  20  is pulled out along an arrow a wherein this pullout establishes the inflow  43  that is directed into the packaging container  10 . However, the inflow  43  cannot come into the basically tube-shaped packaging material  10  without passing the cloud  22 . The cloud forms an aseptic barrier  95 , shown as a plane in dashed line, between the sterilized interior surface of the packaging material and the emitter  20 . The speed of the emitter  20  along the arrow a is slow enough so that the inflow  43  is sterilized by the cloud  22 . 
         [0088]    Of course, as mentioned before, it is also possible to alternatively move the packaging container  10  along the axis A without moving the emitter  20  (emitter being stationary). Alternatively, both the emitter  20  and the packaging container  10  can be moved along the axis A, i.e. the relative movement is performed by both. Advantageously, the movement profile in between the emitter  20  and the basically tube shape packaging material  10 , or in general the packaging material  10 , is adapted so that the flow  42  of the medium in between the emitter  20  and the packaging material  10  is sterilized. 
         [0089]      FIG. 6  shows basically the same embodiment as shown in  FIG. 4 . However, the emitter  20  is already outside the tube-shaped packaging material  10 . Similar to  FIG. 5 , there may still be an inflow  43  directed into the packaging container  10 . The cloud  22  is adapted to sterilize the inflow  43  that comes via the opening  12  into the basically tube-shaped packaging material  10 , and the inflow  43  cannot access the area underneath the aseptic barrier  95  without first being sterilised. In one or more embodiments the movement profile is adapted to hold the arrangement as shown in  FIG. 6  for a certain time to make sure that the inflow  43  is sterilised by the cloud  22 . This means that the relative speed between the packaging material  10  and the emitter  20  can be lowered or also shortly stopped to ensure the sterilization of the inflow  43 . 
         [0090]      FIG. 7  shows an embodiment that is similar to the ones shown in  FIGS. 5 and 6 . However, it is shown that a width w and a length l of the cloud  22  are adapted to make sure that the inflow  43  is sterilized. Compared to  FIG. 6  it is obvious that the width w of the cloud  22  is bigger than a diameter d of the packaging container  10 . The size of the cloud  22  can be adapted using an appropriate power supply to adapt the energy level of the charge carriers and/or its speed or its output dose rate, respectively. 
         [0091]    The invention can be applied in for example a sterilization device as described in the international application No. PCT/EP2013/076870 filed by the applicant. During interior sterilization of the packaging containers a relative movement is made between the packaging container and the emitter. 
       REFERENCE NUMERALS 
       [0000]    
       
           10  (basically tube shaped) packaging material, packaging container 
           10   a  sleeve body 
           10   b  top portion 
           12  opening 
           14  gap 
           20  emitter 
           20   a  first cylindrical body 
           20   b  second cylindrical body 
           22  cloud 
           24  electron exit window 
           26  packaging container opening 
           42  flow 
           43  inflow 
           44  outflow 
           90 ′,  90 ″ movement profiles 
           91  run-in 
           92  run-out 
           95  aseptic barrier 
         x x-axis 
         y y-axis 
         y max  maximum lift, distance in between the first and the second position 
         w width 
         l length 
         A axis 
         a arrow 
         d diameter of the packaging container