Closure with safety feature

Abstract

Disclosed is a closure for a container wherein the container may experience an excessive buildup of internal pressure. The closure is equipped with a “blowout” portion which partially separates from the remaining closure portion if internal pressure exceeds a predetermined limit. The separation occurs at a line of weakness. The line of weakness is specially designed to withstand external, incidental pressure resulting from normal handling yet fracture in a controlled fashion should internal pressure exceed a predetermined amount. In this way inconvenience and possible hazard is avoided from a closure completely separating from the container from excessive pressure.

1 . A closure having a top sized to cover and seal a container orifice, wherein said top comprises a pressure relief portion, said pressure relief portion joined to the remainder of said top through a frangible line of weakness. 
     
     
         2 . A closure as in  claim 1  wherein said line of weakness is designed to resist external pressure on said pressure relief portion and to fracture in a controlled fashion in response to pressure on said pressure relief portion exceeding a predetermined value. 
     
     
         3 . A closure as in  claim 2  wherein said line of weakness varies in strength along its length. 
     
     
         4 . A closure having a top and a skirt depending from a peripheral edge of the top and further comprising a breakaway portion joined by a line of weakness to an annular peripheral portion defined on the top, wherein the breakaway portion includes a first extending portion extending towards the annular peripheral portion and wherein the annular peripheral portion includes a second extending portion extending towards the breakaway portion, the first and second extending portions overlapping to define an overlapping region. 
     
     
         5 . The closure of  claim 4  further comprising: a seal plug depending from a bottom surface of the top, the seal plug shaped to form a hollow cylinder and having a smooth external surface intended to seal against an internal surface of a container neck. 
     
     
         6 . The closure of  claim 5 , wherein the first extending portion of the breakaway portion overlaps on top of the second extending portion of the annular peripheral portion, wherein pressure applied downwards on the top causes the seal plug to press against the internal surface of a container neck placing the overlapping region in compression an insufficient force for tearing the line of weakness, whereas pressure applied upwards on the bottom surface places the overlapping region in tension such that the line of weakness is capable of tearing. 
     
     
         7 . The closure of  claim 4 , wherein the breakaway portion has a disk shape. 
     
     
         8 . The closure of  claim 4 , wherein the line of weakness extends as an arcuate line of weakness. 
     
     
         9 . The closure of  claim 4 , wherein the line of weakness extends in an arc less than 360 degrees. 
     
     
         10 . A closure having a top, a skirt depending from a peripheral edge of the top, and a seal plug depending from a bottom surface of the top, the seal plug shaped to form a hollow cylinder and having a smooth external surface intended to seal against an internal surface of a container neck, the closure further comprising:
 a breakaway portion joined by a line of weakness to an annular peripheral portion defined on the top, wherein the breakaway portion includes a first extending portion extending towards the annular peripheral portion and wherein the annular peripheral portion includes a second extending portion extending towards the breakaway portion, the first and second extending portions overlapping to define an overlapping region,   and wherein the first extending portion of the breakaway portion overlaps on top of the second extending portion of the annular peripheral portion, wherein pressure applied downwards on the top causes the seal plug to press against the internal surface of a container neck placing the overlapping region in compression an insufficient force for tearing the line of weakness, whereas pressure applied upwards on the bottom surface places the overlapping region in tension such that the line of weakness is capable of tearing.   
     
     
         11 . The closure of  claim 10 , wherein the line of weakness extends as an arcuate line of weakness.