Pressure Relief Valve with High Pressure Opening and Closing Functionality

Abstract

One-way pressure relief valves with structure providing high pressure opening and closing functionality are disclosed. Valves of the types described herein may be applied to a product package with flexible walls, for example a package containing dry roasted coffee, to allow gas to escape from the package while preventing entry of ambient air into the package. The valve structure provides a high-pressure valve which both opens and closes at high pressure internal to the package. The valve structure eliminates or reduces excessive expansion of the flexible-walled package caused by pressure increases within the package and eliminates or reduces excessive contraction or paneling of the flexible-walled package caused by increases in ambient pressure outside the package providing for an aesthetically improved package while also maintaining the quality of the packaged product.

What is claimed is: 
     
         1 . A one-way pressure relief valve for relieving pressure within a closed flexible-walled package containing gas-producing goods that both opens and closes under conditions of high pressure within the package, the valve comprising:
 a base layer defining a plane and having a first side, a second side, an area, and a peripheral edge, the base defining a vent extending entirely through the base;   a cover layer overlying the base, the cover layer having a first side, a second side, a width dimension, a thickness dimension of about 0.001 inch to about 0.020 inch between the first and second sides, an area, a peripheral edge generally co-extensive with the base peripheral edge, and a pair of attachment regions secured to the base layer at spaced apart locations of the cover layer;   a dry strap entirely overlying the vent between the base layer, the cover layer, and the attachment regions of the cover layer, the dry strap having a first side, a second side, an area, a thickness dimension of about 0.0005 inch to about 0.002 inch between the first and second sides, a width dimension less than the width dimension of the cover layer enabling location of the dry strap between the attachment regions, and a length dimension extending from one peripheral edge portion of the cover layer to proximate an opposite peripheral edge portion of the cover layer; and   a wetting fluid disposed between the dry strap and the first side of the base layer,   
       wherein, the valve opens when pressure inside the package exceeds ambient pressure by about 0.725 psig to about 1.450 psig and the valve closes when pressure inside the package exceeds ambient pressure by about 0.145 psig to about 0.725 psig, thereby allowing excess pressure within the package to be relieved while retaining sufficient pressure within the package to limit paneling of the package responsive to an increase in ambient pressure relative to the pressure within the package. 
     
     
         2 . The pressure relief valve of  claim 1  wherein, the valve opens when pressure inside the package exceeds ambient pressure by about 0.870 psig to about 1.160 psig and the valve closes when pressure inside the package exceeds ambient pressure by about 0.363 psig to about 0.653 psig. 
     
     
         3 . The pressure relief valve of  claim 2  wherein, the valve opens when pressure inside the package exceeds ambient pressure by about 0.943 psi to about 1.015 psi and the valve closes when pressure inside the package exceeds ambient pressure by about 0.435 psig to about 0.580 psig. 
     
     
         4 . The pressure relief valve of  claim 1  wherein, a ratio of the valve opening pressure to the valve closing pressure is about 2 to about 5. 
     
     
         5 . The pressure relief valve of  claim 4  wherein, the ratio of the valve opening pressure to the valve closing pressure is about 1.78 to about 2.4. 
     
     
         6 . The pressure relief valve of  claim 4  wherein the cover layer, base layer, and dry strap each have a rectangular shape. 
     
     
         7 . The pressure relief valve of  claim 4  wherein the dry strap has a thickness dimension of between about 0.0005 inch to about 0.002 inch. 
     
     
         8 . The pressure relief valve of  claim 7  wherein the dry strap has a width dimension of about 0.125 inch to about 0.25 inch. 
     
     
         9 . The pressure relief valve of  claim 8  wherein the dry strap has a width dimension of about 0.185 inch. 
     
     
         10 . The pressure relief valve of  claim 8  wherein the cover layer has a thickness dimension of about 0.001 inch to about 0.007 inch. 
     
     
         11 . The pressure relief valve of  claim 4  wherein the base, the dry strap, and the cover are of a material selected from the group consisting of polyethylene, polypropylene, and polyester. 
     
     
         12 . The pressure relief valve of  claim 4  wherein the wetting fluid has a viscosity of about 100 centipoise to about 500 centipoise. 
     
     
         13 . The pressure relief valve of  claim 12  wherein the wetting fluid has a viscosity of about 350 centipoise. 
     
     
         14 . The pressure relief valve of  claim 12  wherein the wetting fluid is present in an amount of about 1.5 μL to about 2.3 μL. 
     
     
         15 . The pressure relief valve of  claim 14  wherein the wetting fluid is selected from the group consisting of silicone oil, graphite-impregnated oil, food grade oil, and food grade silicone grease. 
     
     
         16 . The pressure relief valve of  claim 4  wherein the vent defined by the base has a total cross-sectional area in the plane of less than about 0.00283 in 2 . 
     
     
         17 . The pressure relief valve of  claim 16  wherein the vent defined by the base has a total cross-sectional area in the plane of about 0.0000785 in 2  to about 0.00283 in 2 . 
     
     
         18 . The pressure relief valve of  claim 16  wherein each opening has a diameter in the plane of about 0.010 inch. 
     
     
         19 . The pressure relief valve of  claim 18  wherein the vent defined by the base includes from one to nine openings entirely through the base. 
     
     
         20 . The pressure relief valve of  claim 1  further including an adhesive securing the attachment regions of the cover layer to the base layer, the adhesive being selected from the group consisting of pressure-sensitive adhesives (PSAs), heat-activated adhesives, ultraviolet cured adhesives, water-based adhesives, solvent-based adhesives, and rubber-based adhesives. 
     
     
         21 . The pressure relief valve of  claim 1  in combination with a flexible-walled package containing gas-producing roasted coffee, the package being selected from the group consisting of a paperboard package and a polymer package.