Abstract:
A one-way degassing valve ( 4 ) for containers of aromatic products such as coffee and the like, comprising a valve body ( 5, 6 ), a valve element ( 12 ) and a filter ( 17 ), comprising a selective filter layer ( 21   a ), preferably consisting of activated charcoal, which allows the passage of low molecular weight gases, such as carbon dioxide, and retains high molecular weight gases that constitute the product&#39;s aroma, and an oxygen and CO 2  adsorbing layer ( 21   b ), able to eliminate the residual oxygen present in the container and suitably reduce the amount of CO 2 .

Description:
FIELD OF THE INVENTION 
     present invention relates to a valve for containers of aromatic or in any case odorous products, especially particulate or powder products, such as coffee, detergents, organic liquids and the like. 
     BACKGROUND OF THE INVENTION 
     Valves of the above-mentioned type are obviously already known and are commonly called degassing valves. They are one-way valves which are normally applied to the upper wall of the container and whose purpose is to allow the gases developed by the product, for example coffee, to escape from the container, avoiding the possible build-up of internal overpressure, which would cause bulging and/or tearing of the container itself, and at the same time to prevent air from entering the container as this would impair the quality of the product. 
     The one-way valves used at present serve this purpose perfectly, opening when slight internal overpressures occur and closing immediately when they cease. 
     However, these valves present great drawbacks due to the following considerations. 
     Fresh (newly packaged) coffee generates a mixture of gases inside the container, consisting mainly of carbon dioxide and, in a smaller percentage, of so-called aromas, which are characterized by complex molecular chains. 
     The one-way valves currently in use utilize porous filters, whose sole purpose is to prevent the escape of particles of coffee. In the event of overpressures inside the container, therefore, they allow both carbon dioxide and the product&#39;s aromas to escape, as well as other gases. Valves of this type are described, for example, in Italian patents 823800 and 971505. 
     Although specific reference is made in this description to coffee, that is to a product with a pleasant aroma, the same problem arises for odorous products in general, such as the detergents and organic liquids mentioned above, for which it would be desirable to avoid the escape of odours, in this case unpleasant ones. 
     EP-0 659 657 B1 describes a valve of the selective type which allows the gases that form in the package to escape, retaining the product&#39;s aromas. It has been noted, however, that such a type of valve does not allow the complete escape of the oxygen, which tends to oxidize the product with which it comes into contact, detracting from the quality thereof. 
     It is therefore necessary to close the container after having created a high vacuum by a procedure that tends to slow down the production rates of the packaging machines or else it is necessary to carry out washing with inert gas, again by means of quite a costly procedure. 
     The package has a slightly bulging appearance according to the overpressure necessary for opening the valve. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to avoid said drawbacks, and to preserve the nature of the product more or less intact, reducing to a minimum or preventing the escape of aromas or odours, and at the same time ensuring that the oxygen present in the package is eliminated and the carbon dioxide is reduced so that the package does not appear to bulge. 
     This object is achieved, according to the invention, by providing a degassing valve equipped with a selective filter, which allows the passage of molecules of carbon dioxide and other gases, and traps the molecules that determine the product&#39;s aroma and odours, not allowing them to escape, and which eliminates the residual part of the oxygen, thus enhancing the quality of the product. 
     Coffee is known to develop a large amount of CO 2 , equivalent to as much as two or three times its volume, after toasting. Most of this CO 2  is eliminated through the valve, whereas the residual amount is absorbed by the filter to such an extent as to further reduce the residual internal pressure inside the package, thereby giving the package a pleasant appearance without bulges. 
     Porous filters or molecular sieves can be used as selective filters. However, in the tests performed it has been observed that the filters that best perform this selector function are compounds based on activated charcoal, diatomaceous earth, silica, etc, which in any case can be modified by adding additives which make them specific to the individual organic requirements. The oxygen, on the other hand, is adsorbed through oxidoreduction reactions, reactions of addition to organic substances, as already known to the art. The same applies to CO 2 . 
     Further characteristics of the invention will be made clearer by the detailed description that follows, referring to a purely exemplary and therefore non-limiting embodiment thereof, illustrated in the appended drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded diagrammatic view of a degassing valve equipped with a selective, oxygen-adsorbing filter according to the invention. 
     FIG. 2 is a diagrammatic sectional view of the valve in FIG. 1, installed on a container, shown partially; 
     FIG. 3 is a diagrammatic axonometric view of a container equipped with such a valve. 
     FIG. 4 is a diagrammatic side elevational view of a degassing valve according to the invention before installation on a container. 
    
    
     DESCRIPTION OF THE INVENTION 
     With reference to these figures, in FIG. 3 reference numeral  1  designates in a general way a container for aromatic products, particularly coffee, of the flexible or semi-rigid type. 
     In the example illustrated, the selective valve according to the invention is installed on the front part of the container. For this purpose, a small hole  3  is made in the sheet material, or laminate, of the container, beneath which a degassing valve, designated as a whole by reference numeral  4 , is applied, said valve being heat-welded or glued to the laminate  2 . 
     The degassing valve  4 , whose general structure can be considered substantially known, comprises a base plate  5  and a cap  6  seated therein. The cap  6  has near its lower edge an annular groove  7  which engages in a corresponding annular projection  8  provided on the bottom of the plate  5 . Above the projection  8  is a flat annular wall  9 , which surrounds a central disk  10  provided with holes  11 . 
     Between the cap  6  and the plate  5  is interposed a rubber diaphragm  12  acting as the valve proper, the peripheral part of which rests on said flat annular wall  9  of the plate, which is spread with a viscous layer  13 , in order to provide a better seal. The diaphragm  12  is pressed against the plate  5  by an opposing projection  14  provided in the upper wall of the cap  6 , in which a bleed or vent hole  15  is also provided. 
     The bottom of the plate  5  is shaped so that underneath it, below the disk  10 , a seating  16  is provided for a filter  17  that will be described in greater detail below. 
     The valve  4  is fixed to the sheet  2  by welding or gluing that follows an annular path  18  along the upper outside edge of the plate  5 . 
     The valve works as follows. 
     Under normal conditions, the rubber diaphragm  12  is applied in abutment against the flat wall  9  of the plate  5  and, thanks to the presence of the viscous layer  13 , creates a seal both against the escape of the gases contained inside the container  1 , and against the entry of air from the outside. 
     In the event of overpressures inside the container  1 , the diaphragm  12  lifts from the wall  9 , allowing the gases to escape, passing through the holes  11 , the space that is created between the diaphragm  12  and the wall  9 , the hole  15  in cap  6  and the hole  3  formed in the laminate  2  into the outside environment. When normal conditions are restored, the diaphragm  12  comes down again, preventing air from entering the container by the opposite route to that previously described. 
     In order to prevent the coffee aromas from escaping when the gases are being discharged from the container, a selective type filter  17  is used, comprising a plurality of porous layers with interposed adsorbent layers. 
     In the preferred embodiment illustrated in FIG. 1, the filter  17  comprises an upper porous disk  19   a , beneath which is disposed an adsorbent layer of activated charcoal  21   a , a second porous disk  20 , then an oxygen and CO 2  adsorbing layer  21   b , consisting of materials containing ferrous ions, for example, and a third porous disk  19   b . The whole can be retained in the seating both by simple pressure and by gluing or welding of a filtering wall. 
     The adsorbent layer  21   b  is disposed more to the inside of the package, that is, nearer to the product, to improve the reduction of oxygen and CO 2  in the package. 
     According to an alternative embodiment, the two adsorbent layers  21   a  and  21   b  can be incorporated into a single layer comprising both activated charcoal and a substance that adsorbs oxygen and CO 2 , thus eliminating one porous disk. 
     Another alternative consists in making two side-by-side chambers in the seating recess  16 , said chambers separately containing the activated charcoal or the like and the oxygen and CO 2  adsorbent. In this case the chamber containing the oxygen adsorbent may even not be in communication with the upper area of the valve, since it has the sole function of adsorbing the oxygen and CO 2 . 
     In order to preserve the activity of the adsorbents and in particular of the oxygen adsorbent, which would degrade rapidly upon contact with air, these are suitably protected before being installed on the package, for example by means of an underlying impermeable layer. This could consist of a multi-layer laminate composed, for example, of a peel-away polyester, aluminium and polyethylene film  24 , as shown schematically in FIG.  4 . In this case a ribbon or tape  24  would be obtained, on which the valves are welded and this would serve as a loader for the valves on the packaging lines. The ribbon of barrier film would be detached from the valve at the time of application to the desired point of the package. Alternatively, the ribbon of barrier film can be punched onto the valve and remain welded thereto, to be perforated at the time of application of the valve to the package, thus preventing contact with the oxygen before the adsorbent begins to do its work. 
     With a filter thus structured, the gases given off by the coffee, before passing through the rubber diaphragm  12 , are filtered through the activated charcoal  21   a , which retains the majority of them, that is the aromas, thus maintaining a higher concentration inside the package. At the same time, the oxygen and CO 2  adsorbent  21   b  eliminates the oxygen present in the package and maintains a suitable CO 2  content, eliminating the overpressure necessary to open the valve. 
     The role of the CO 2  adsorbent is thus to eliminate the overpressure present in the bag after the degassing procedure performed by the valve, in order to make the pressure inside and outside the package equal, eliminating bulging. 
     Application of the selective filter essentially acts as a barrier against the escape of volatile organic substances (aromas, fragrances, odours, etc.) from inside the container through degassing of the product. The filter component that removes the oxygen present in the package allows oxidization of the contents to be reduced, increasing the product&#39;s shelf life. 
     The system described above can find a use whenever it is necessary to allow gases to escape from the package, avoiding the passage of organic molecules and also reducing the oxygen and CO 2  content.