Abstract:
The invention relates to a pressure relief valve, comprising a base body, which is covered by a valve membrane. The base body which is located on the inner face of a packaging container, permits the escape of excess pressure from the packaging container into the atmosphere by means of passages and perforations that are configured in the wall of the packaging material. The inventive pressure relief valve thus responds particularly well. i.e. allowing particularly low opening pressures, by means of the special configuration of its base area.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a 35 USC 371 application of PCT/EP2005/054464 filed on Sep. 8, 2005. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a pressure relief valve for a packaging container. 
   2. Description of the Prior Art 
   DE 102 56 245 A1 has disclosed a pressure relief valve in which, in the region in which it overlaps with the base body, the valve membrane is always spaced the same distance apart from it except in the region of a recess. This makes it possible to achieve a very good seal, i.e. outside air cannot get into the interior of the packaging container. This is due to the fact that the flat contact of the valve membrane against the base body permits the sealant in the form of silicone oil between the base body and the valve membrane to provide relatively powerful adhesion forces between the valve membrane and the base body. In order to enable the pressure relief valve to better react to the occurrence of an excess pressure inside the package due to the generation of gases, however, it is necessary for the pressure relief valve to have the lowest possible opening pressure, i.e. the valve membrane should lift away from the base body extremely easily in order to produce a through conduit. 
   SUMMARY AND ADVANTAGES OF THE INVENTION 
   The pressure relief valve for a packaging container according to the invention has the advantage that it opens even at relatively low excess pressures inside the package (for example on the order of magnitude of 5 mbar), i.e. it conveys gases generated inside the package to the outside even at a relatively low excess pressure This is achieved according to the invention essentially through an embodiment of the base body that is not flat at least in some areas of the region in which it overlaps with the valve membrane. This reduces the adhesion forces between the base body and the valve membrane generated by the sealant between them and thus facilitates the lifting of the valve membrane. 
   Advantageous modifications of the pressure relief valve for a packaging container according to the invention are disclosed. It is particularly advantageous for the at least one through hole provided at the bottom of the base body in the region of the recess to be encompassed by a rim-like raised area. As a result, the atmospheric pressure that acts on the valve from the outside presses the valve membrane against the raised area in the region of the at least one through hole, thus closing the through hole and reliably preventing external air from penetrating into the interior of the package. 

   
     DRAWINGS BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are described more fully herein below, with reference to the drawings, in which: 
       FIG. 1  is a longitudinal section through a first pressure relief valve according to the invention, in the region of a packaging material wall of a packaging container, 
       FIG. 2  is a top view of the pressure relief valve in  FIG. 1 , 
       FIG. 3  shows a detail of the pressure relief valve in  FIG. 1  in the vicinity of the edge region of the pressure relief valve, 
       FIG. 4  shows a detail of the pressure relief valve in  FIG. 1  in the vicinity of a tower-like raised area, 
       FIG. 5  is a top view of a second pressure relief valve according to the invention, 
       FIG. 6  is a section in the plane VI-VI of  FIG. 5 , 
       FIG. 7  is a top view of a third pressure relief valve according to the invention, 
       FIG. 8  is a section in the plane VIII-VIII of  FIG. 7 , and 
       FIGS. 9 and 10  show top views of other pressure relief valves according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a first pressure relief valve  10 . The pressure relief valve  10  is attached to the inside  2  of a packaging material wall  1 , which, through appropriate folding and sealing, forms a packaging container or packaging pouch for packaging gas-emitting foods such as coffee. 
   The pressure relief valve  10  has a round base body  11  manufactured of plastic by means of the injection-molding process. The base body  11  has a circumferential edge region  12  whose end surface oriented toward the inside  2  of the packaging material wall  1  has a circumferential, cross-sectionally triangular protrusion  13  formed onto it. The protrusion  13  permits the base body  11  to be fastened to the inside  2  of the packaging material wall  1  in a sealed fashion by means of ultrasonic welding. It should also be noted that in lieu of a protrusion  13  and fastening by ultrasonic welding, it is also possible for conventional adhesives or a contact sealing process to be used in order to fasten the edge region  12  of the base body  11  to the inside  2  of the packaging material wall  1  in a sealed fashion. 
   In the region of the packaging material wall  1  enclosed by the edge region  12 , preferably several holes, incisions, or perforations  5  are provided in the packaging material wall  1 , which permit the gas produced by the food to escape to the outside of the package, i.e. to the surrounding air. 
   The base body  11  has a base region  15  that is recessed in relation to the edge region  12 . On the side oriented toward the packaging material wall  2 , the base region  15  is not planar or flat, but is instead curved. Preferably, a concave curvature is used so that the central region  16  of the base region  15  is spaced a greater distance apart from the packaging material wall  2  than the outer region  17  of the base region  15 . In addition, as can best be seen by looking at both  FIG. 1  and  FIG. 2 , the central region  16  also has a recess  20  on the side oriented toward the packaging material wall  2 . Viewed from above ( FIG. 2 ), the recess  20  is approximately the shape of a figure “8”. On both sides of the constricted region  21  of the recess  20 , the recess  20  contains a respective through hole  23 ,  24  that communicates with the package interior. On the side oriented toward the recess  20 , each of the two through holes  23 ,  24  is encompassed by a rim-like raised area  25 ,  26 , which is circular when viewed from above. As can best be seen in  FIG. 4 , each of the two raised areas  25 ,  26  has an inlet radius  4 ; the upper end surface  28 ,  29  of the raised area  25 ,  26  extends at a level situated just below the height of the base region  15  immediately adjacent to the recess  20 . 
   It should also be noted at this point that the raised areas  25 ,  26  can also rise up to the level of the base region  15  in the central region  16 , or can even extend beyond it. 
   On the outer, circumferential edge of the base region  15 , an additional recess  30  is provided, which extends to the edge region  12 . In addition, the side of the base body  11  oriented away from the packaging material wall  2  has a preferably round hollow  32 , which extends over the two through holes  23 ,  24  and in which a filter element  34  in the form of a nonwoven or the like material is fastened. The nonwoven material  34  serves to prevent food particles from getting into the through holes  23 ,  24  and clogging them when the particle size is greater than the diameter of the through holes  23 ,  24 . 
   A sealant in the form of a thin silicone oil layer  36  is applied in the vicinity of the base region  15 . The silicone oil layer  36  serves as a sealant and fastening agent between the base body  11  and a likewise preferably round valve membrane  40 . The diameter of the valve membrane  40  is slightly smaller than the inner diameter delimited by the edge region  12  of the base body  11 . 
   The valve membrane  40  is likewise comprised of plastic and based on the selected thickness, is flexible to a certain degree. In order to prevent the valve membrane  40  from falling out of the base body  11 , in the exemplary embodiment, a circumferential constriction  41  is formed onto the base body  11  on the inside of the edge region  12 . In lieu of a circumferential constriction  41 , however, it is also conceivable to use retaining fingers or the like, which are only provided in some areas. 
   The pressure relief valve  10  described up to this point functions as follows: the gas that the food produces during storage due to chemical transformation processes increases the internal pressure of the package until it ends up being greater than the atmospheric pressure surrounding the package. As soon as this excess pressure has reached a magnitude of 5 mbar, for example, it causes the valve membrane  40  to lift up initially in the region of the two points  43 ,  44  of the constriction region  21  of the recess  20 . Leading from there, at least one conduit-like passage is formed in the direction toward the edge region  12  of the base body  11  until the gas can escape via the outer edge of the valve membrane  40 . From there, the gas travels through the perforations  5  to the outside of the package and into the surrounding air. As soon as the excess pressure has been reduced, the valve membrane  40 , starting from its edge region, lies back down against the base body  11 , whereupon the silicone oil layer  36 , due to its adhesion forces, produces a seal that also prevents the entry of surrounding air into the inside of the package. 
   In the context of the invention, the lifting of the valve membrane  40  is facilitated in that in the central region  16  that also contains the recess  20 , the distance of the base region  15  from the valve membrane  40  is relatively large due to the concave design of the base region  15 , so that (due to the rigidity of the valve membrane  40 ) the adhesion forces between the valve membrane  40  and the base body  11  are reduced in relation to those in the outer region  17 . This facilitates the lifting of the valve membrane  40  in the region of the points  43 ,  44 . The pressure relief valve  10  described up to this point therefore permits gas to escape from the inside of the package at a relatively low excess pressure (in relation to the environment). In addition, the pressure relief valve  10  seals particularly well in relation to the outside since the atmospheric pressure acting on the valve membrane  40  via the perforations  5  additionally presses the valve membrane  40  against the two raised areas  25 ,  26 , thus closing the through holes  23 ,  24 . In addition, the circumferential recess  30  permits silicone oil to collect in this region and this region serves as a reservoir for silicone oil, which can therefore be resupplied to the valve membrane  40  so that a relatively uniform wetting of the valve membrane  40  with the silicone oil occurs on the side oriented toward the base region  15 . 
   In the second pressure relief valve  50  show in  FIGS. 5 and 6 , an outwardly tapering hollow  52 ,  53  extends out from both sides of the recess  51 . Outside the two hollows  52 ,  53 , the base region  55  of the base body  56  is embodied as planar or flat. Because the two hollows  52 ,  53  extend outward from the two points  57 ,  58  of the likewise figure “8”-shaped recess  51 , this permits the valve membrane  59  to lift up particularly easily in the second pressure relief valve  50  as well. 
   In the third pressure relief valve  60  shown in  FIGS. 7 and 8 , the recess  61  is embodied as circular in accordance with the first pressure relief valve  10 , but extends only to the edge of the recess  62 . 
   In the pressure relief valves  65  and  66  show in  FIGS. 9 and 10 , no recess or the like is provided in the vicinity of the base region  67 ,  68  and instead, for example, two elongated stays  69  ( FIG. 9 ) or a protrusion  70  ( FIG. 10 ), manufactured by being injection molded in place, produce a greater distance between the base body  67 ,  68  and the valve membrane covering over the base body  67 ,  68 . Consequently, in the regions of both the stays  69  and the protrusion  70 , the adhesion forces between the base body  67 ,  68  and the valve membrane are likewise reduced in order to make for an easier lifting of the valve membrane and thus a better reaction of the pressure relief valve  65 ,  66  in the event of an excess pressure inside the package. 
   The pressure relief valves  10 ,  50 ,  60 ,  65 , and  66  described up to this point can be modified in a multitude of ways without going beyond the concept of the present invention. This concept in particular is comprised of making it easier for the valve membrane to lift through a particular embodiment of the respective base region and overlap region with the valve membrane by increasing the distance between the valve membrane and the base body. 
   The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.