Abstract:
A sterilization system for use with a form, fill, seal machine to sterilize the web material being processed by the machine. The web passes seriatim through an ionized air wash, a chemical pre-wash, a sterilant bath, squeeze rollers, hot air knives and a UV radiation source. The synergism of the respective in-line treatments facilitates efficient sterilization at high web feed rates.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a sterilization system and method for a web of material being fed to a form, fill and seal packaging machine. More specifically, the present invention relates to a sterilization system and method, which achieves high sterilization efficiencies for high-speed web feed rates into the machine.  
           [0003]    2. Description of Related Art  
           [0004]    Heretofore, the forming, sealing and filling of flexible packages, and particularly aseptic packages, have been performed by various techniques and apparatus. But, due to the nature of the packages to be filled and formed, and the aseptic environmental requirements, conventional systems have not been able to produce aseptic shelf-stable products at high speeds.  
           [0005]    It is desirable to achieve above 300 packages/min, preferably above 600 packs/min, 80 to 85% efficiency of the filling line, but heretofore such speeds have not been achievable. Accordingly, a need in the art exists for a system and method for continuously forming, sealing and filling flexible packages at increased rates of speed as compared to prior techniques and systems.  
           [0006]    However, the faster the rate of speed, the achievement of satisfactory sterilization levels becomes more problematic, since the residence time of the web at any sterilization station decreases with increased feed rates.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, it is a primary aspect of the present invention to provide a sterilization system and method having increased sterilization efficiencies, thus permitting use in high-speed form, fill and seal packaging machines.  
           [0008]    It is a primary goal of the present invention to achieve up to a cumulative 5-log reduction of highly resistant spores, such as  Bacillus subtilis,  or other microorganisms on the web for aseptic use due to the synergies of the combined sterilization steps.  
           [0009]    The aspects of the present invention are generally fulfilled by providing an apparatus for sterilizing web material being fed to a package form-fill-seal machine comprising:  
           [0010]    a first bath of liquid chemical, such as an acid solution for pre-washing the web passing therethrough;  
           [0011]    a second bath of liquid sterilant for sterilizing the web passing therethrough;  
           [0012]    a cleaning device for removing excess sterilant from the web emerging from the bath; and  
           [0013]    a feeding device for transporting the web material through the first and second baths of acid and sterilant, and the cleaning device.  
           [0014]    The apparatus further includes a first recirculation device for feeding the acid solution adjusted to an appropriate concentration back to the first bath by a feedback conduit between an output of the first bath and an input thereof, and a first recirculation bath connected therein, said first recirculation bath having an input for accommodating the introduction of an additional pre-wash chemical.  
           [0015]    A second recirculation device for feeding liquid sterilant back to the second bath may also be provided by a feedback conduit between an output of the second bath and an input thereof, and a second recirculation bath in the feedback conduit having an input for accommodating the introduction of additional sterilant.  
           [0016]    The pre-wash acids in a preferred embodiment may be citric or acetic acid. The pre-wash station could also contain ozonated water for aseptic applications.  
           [0017]    The liquid sterilant may be H 2 O 2 , ozonated water, or combinations thereof.  
           [0018]    The web material for making packages in accordance with the present invention may be formed from plastic, laminates of plastic, flexible foil laminates, combinations of foil and plastic, paper and plastic composite materials, or any other suitable flexible materials.  
           [0019]    The packages may be filled with preserved hot or cold sterile liquids, such as citrus juices, low acid beverages, such as milk products, teas, coffees, and particulate material including citrus pulp or fruit particles.  
           [0020]    Also provided, in combination with the aforementioned features of the apparatus of the present invention, are pretreatment and post-treatment stations. At the input end there is provided an ionized air treatment station for the web. At the output end, squeegee rolls, hot air knives and an UV irradiation unit are provided to provide post-treatment to the web as it exits the sterilant bath.  
           [0021]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
         [0023]    [0023]FIG. 1 is a schematic block diagram of an overall form, fill, and seal system in which the sterilizing system of the present invention is utilized;  
         [0024]    [0024]FIG. 2 is a schematic block diagram depicting the in-line components of the sterilization system and method of the present invention; and  
         [0025]    [0025]FIG. 3 is a perspective view of a preferred embodiment of the mechanical configuration of the sterilization system of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0026]    [0026]FIG. 1 discloses the package forming and sterilization mechanisms of the system and method of the present invention. The sheet material from which the web W is formed may be provided on a package roll-stock feeder  6 . The web W then proceeds through a sterilization mechanism  7 . The web W emerges from sterilizer  7 , and travels through a pouch side-sealing turret  8 , which forms side seams of the pouches P. The web W passes around an idler roller  9  to the perimeter of a cold pouch-filling machine  11 . Filled pouches on the web W emerging from filler  11  pass on through a continuous ultrasonic top sealer  18 , which seals the top opening of the filled packages. At this point, the packages may pass from the aseptic or ultra-clean environment to merely a clean environment because the packages with sterile liquid or other materials therein have been hermetically sealed. Emerging from sealer  18 , web W passes through a straw applicator  20 , which may secure a straw to each package. The web W then passes through a die  22  puncture or cutter, and the sealed packages are separated into individual packages for processing by secondary packages  30 , which may form cases, multi-paks, and so forth at speeds of about 720 ppm.  
         [0027]    The sterilization system  7  is depicted in more detail in the block diagram of FIG. 2. As illustrated therein, the web W moves from left to right through a series of stations for treating the web. At the input end there is provided an ionized air rinse station  40 . Following station  40  is a pre-wash bath  42  containing citric acid or acetic (tartaric, lactic, malic or other organic acids) acid. The pre-wash bath  42  also has a recirculation conduit  42 R with a recirculation tank  42 T connected therein. Following the pre-wash bath  42 , is sterilant bath  44  containing H 2 O 2  or ozonated water. Bath  44  also includes a recirculation conduit  44 R with a recirculation tank  44 R therein. The recirculation tanks,  42 T and  44 T, are both provided to facilitate adjustment of the concentration of the liquids in the respective baths  42  and  44  during the recirculation phase of those liquids in order to control the efficiency of the washes. Following the bath  44 , the web W moves through a series of squeegee rolls  46  and hot air knives  48  to remove excess sterilant and chemicals from the web. As a final treatment of the web W, it passes through a UV irradiation station  50  to further sterilize the web before it proceeds to the form-fill machine of FIG. 1.  
         [0028]    Referring in more detail to the system and method illustrated in the block diagram of FIG. 2, at station  40  the ionized air rinse of the web material just before entering the pre-wash bath  42  is effective to prepare the web for treatment in the respective acid and sterilant baths  42  and  44 . This ionized air rinse may reduce the microbial load up to 1 log.  
         [0029]    The pre-wash bath  42  is used depending on what the product to be packaged is, namely, a preserved ambient fill, or a hot-fill, or aseptic ambient fill. Food grade citric, or acetic acid up to 5% (1-3% preferred), can be used in bath  42  to pre-wash the web at a speed of 1 m/s (might go up to 2 m/s). Other acids such as tartaric, lactic and malic, and water could be used in the pre-wash bath  42 . Mechanical washing action at high speeds and the chemicals at 65° C. would help reduce the microbial load by about 1-2 logs. Ozonated water in a recirculation bath  42 T could be used for aseptic applications to enhance the sterilization effect. The temperature in the recirculation bath would be up to 30° C., and the concentration is preferably up to 25 ppm (preferred up to 10 ppm). The exposure time within the pre-wash bath is less than 1-2 s, preferably 1 s, but this varies depending on the speed of the web W.  
         [0030]    The final wash and sterilant bath  44  in a preferred embodiment is hydrogen peroxide based chemicals (hydrogen peroxide, peroxyacetic acid, etc.). For use for aseptic application, it is preferred that the H 2 O 2  concentration is up to 50% at 70° C., and 1-3 seconds exposure time. For different chemicals, the condition will vary. For non-aseptic applications, the pre-wash could utilize acid or water, and the final wash in sterilant bath  44  could have ozonated water. Or in the alternative, the sterilant bath liquid could include a combination of H 2 O 2  and ozonated water.  
         [0031]    At station  46 , excess sterilant is removed by squeegee rolls  46  and hot air knives  48  at temperatures up to 150° C.  
         [0032]    At station  50 , the web is exposed to ultraviolet (UV) light radiation, of 200-260 nm, or preferably 254 nm from low or medium pressure lamps. The UV treatment may be for up to 3 s exposure (up to 200 mJ/sq cm preferred), but such may be expensive and practically difficult to achieve. So, in any event, the UV treatment should provide at least 100 mJ/sq.cm.  
         [0033]    Referring to FIG. 3, which depicts a preferred embodiment of the mechanical configuration of the system depicted in FIG. 2, the stations  40 ,  42 ,  44 ,  46 ,  50  are shown in-line in the sterilant apparatus  7 . Beginning at the left-hand side of the figure, the ionized air pre-rinse  40  is applied to a web W entering the pre-wash bath  42 . Pre-wash bath  42  is provided with a chemical inlet  42 -l for introducing an acid solution thereinto. Bath  42  is also provided with an outlet  42 -O for connection to recirculation conduit  42 R and tank  42 T of FIG. 2. A series of top-feed rollers  43  and bottom-feed rollers  47  are provided for transporting the web through the liquid in the respective baths  42  and  44  as the web W travels through the sterilizing device to the form, fill, and seal machine. The sterilant bath  44  includes a chemical outlet  44 - 0  for connection to the recirculation conduit  44 R and recirculation tank  44 T depicted in FIG. 2. Circulation bath  44  is also provided with an appropriate inlet on the other side of the apparatus depicted in FIG. 3, but that inlet is not shown for clarity purposes. Suitable circulation pumps (not shown) are also provided at appropriate locations.  
         [0034]    At the output of bath  44 , the squeegee rolls  46  are provided to squeeze excess sterilant and chemicals from the web W. Also provided are hot air knives  48  for further removing excess chemicals from the web. These removed excess chemicals fall into a sloped chemical drain pan  45 , and are returned to the sterilant bath  44  for reuse. Also, since the chemical drain pan  45  passes underneath the web W, volatiles from the sterilant flowing through the drain pan contact the overlying web W, and further enhance sterilization thereof. At the output end of the sterilizer  7  of FIG. 3, suitable ultraviolet (UV) light sources, appropriate reflectors, and unit  50  are provided to perform a final sterilizing treatment of the web before it passes to the form, fill, seal machine.  
         [0035]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.