Pressure relief device

For use with a container having an internally concave closure wall, a pressure relief device comprising:

• an externally protruding impression in said closure wall, said impression having a single weakened line of reduced material thickness partially circumscribing a tab member, said line being adapted to rupture in response to overpressurization of the contents of said container, thus permitting said tab member to deflect outwardly and to create an opening through which said overpressurized contents may be vented to the atmosphere, and
• metering means forcibly seated in said impression for radially outwardly stressing said impression and for reducing the rate at which said contents are vented through said opening.

A pressure release device for a container which is closed at one end by an internally concave bottom wall, said device comprising:

• an externally protruding first cup formed as an impression in said bottom wall, said first cup having a circular first side wall joined at one end to said bottom wall and closed at its outer end by a circular first base portion;
• a tab member formed in said first base portion, said tab member being partially circumscribed by a line of reduced material thickness;
• and a second cup having a circular second wall open at one end and closed at its opposite end by a second base portion, said second base portion having a metering orifice therein which is smaller in area than the area of the first base portion circumscribed by said line of reduced material thickness, said second cup being forcibly received in said first cup, with said circular second wall coacting with said circular first wall to radially prestress said first base portion.