Package provided with a rigid lid and a valve, in particular for cooking food

Abstract

The package is closed by a lid and it is fitted with a valve fixed over an opening zone of section greater than 10 mm 2 , and preferably lying in the range 30 mm 2 to 50 mm 2 , leading to the inside of the package and formed through said lid. This opening zone is either an orifice formed through a flat lid, or else a hollow chamber itself pierced by a vent orifice of small size. The valve comprises solely a flexible sheet extending over the opening zone together with a sealing compound disposed between the flexible sheet and the lid. The sealing compound is solid at ambient temperature and it passes to a non-sticky liquid state when its temperature is raised. During heat treatment, the valve opens and closes in a succession of venting sequences. The valve opens under the effect of the pressure inside the package increasing sufficiently to create an exhaust channel through the sealing compound in the liquid state spread between the lid and the flexible sheet, said channel extending between the opening zone and an edge of the flexible sheet. After partial venting through the exhaust channel, and while the pressure inside the package is still greater than the pressure outside it, the valve is caused to close by said exhaust channel closing due to the cohesion forces between the sealing compound in the liquid state and both the lid and the flexible sheet. On cooling at the end of heat treatment, the sealing compound solidifies and fixes the flexible sheet to the lid, thereby locking the valve in its closed position.

What is claimed is:  
     
         1 / A package fitted with a valve and closed by a lid, said valve being fitted over an orifice leading to the inside of the package and formed through said lid, wherein: 
 a) the lid is made of a material that is rigid or semi-rigid;    b) the valve comprises solely: 
 a flexible sheet extending over an opening zone formed through the lid and including the orifice; and  
 a sealing compound disposed between the flexible sheet and the lid;  
   c) the section of the opening zone is greater than 10 square millimeters (mm 2 ); and    d) wherein the sealing compound is solid at ambient temperature, when it is impermeable to gas, to liquids, and preferably also to microorganisms, and passes to a non-sticky liquid state when its temperature is raised so that during heat treatment the valve opens and closes in a succession of venting sequences, with opening of the valve being obtained under the effect of the pressure inside the package rising sufficiently to create an exhaust channel through the sealing compound then in the liquid state and spread between the lid and the flexible sheet, said channel extending between the orifice and an edge of the flexible sheet, and closure of the valve being obtained, after partial venting via the exhaust channel and while the pressure inside the package is still greater than the pressure outside, by said exhaust channel reclosing due to the cohesion forces between the sealing compound in the liquid state and both the lid and the flexible sheet, so that during cooling after the heat treatment, solidification of the sealing compound fixes the flexible sheet to the lid, thereby locking the valve in the closed position.    
     
     
         2 / A package according to  claim 1 , wherein the opening zone is constituted merely by a vent orifice of section greater than 10 mm 2  formed through a flat lid.  
     
     
         3 / A package according to  claim 1 , wherein the opening zone is constituted by a hollow chamber, e.g. formed by stamping the lid, said chamber being of section greater than 10 mm 2  and being pierced by a vent orifice of smaller section.  
     
     
         4 / A package according to  claim 1 , wherein the opening zone made through the lid has a section of about 30 mm 2  to 50 mm 2 .  
     
     
         5 / A package according to  claim 1 , wherein the flexible sheet is fixed in part to the lid on either side of the opening while leaving at least one unfixed zone.  
     
     
         6 / A package according to  claim 5 , wherein the valve has two unfixed zones opposite each other between the flexible sheet and the lid.  
     
     
         7 / A package according to  claim 1 , wherein the lid is made of metal.  
     
     
         8 / A package according to  claim 7 , comprising a jar and a lid fixed in leaktight manner by being screwed onto the top portion of the jar.  
     
     
         9 / A package according to  claim 1 , wherein the top face of the flexible sheet is fixed, e.g. by adhesive, to a flat element of the label type, itself being fixed in part to the lid on either side of the opening zone, while leaving at least one unfixed zone.  
     
     
         10 / A package according to  claim 1 , including a flat porous element fixed over the orifice on the inside face of the lid.  
     
     
         11 / A package according to  claim 1 , including a tab fixed to or extending the flexible sheet or the flat label-type element.  
     
     
         12 / A package according to  claim 1 , wherein the flexible sheet is made of a material that deforms permanently under conditions of temperature and pressure that are too sudden.  
     
     
         13 / A package according to  claim 12 , wherein the flexible sheet is a sheet of polyester that is less than 25 μm thick.