Noise muffler having a unique pressure safety valve

Claim 1

A noise muffler for reducing the noise level of a noise carrying gaseous discharge from a port, and having a unique safety valve comprising: a housing having a perforated portion providing an outlet path from said housing for gaseous flow and a solid portion impervious to gaseous flow; fitting means adapted to be attached to said port to provide a substantially airtight path between said port and the inside of said housing; a porous material having sufficient thickness and density to break up an acoustic wave and reduce the noise level of said gaseous discharge, said porous material being mounted within said housing in substantially airtight contact with said solid portion so that all gaseous flow from said port must pass through said porous material to reach said perforated portion, said porous material also being spaced from one area of said solid portion so that said gaseous flow from said port strikes said one area without passing through said porous material; a groove formed on said one area of said solid housing portion for causing said solid housing portion to rupture along said groove in response to a predetermined pressure within said housing, said groove having a beginning and an end displaced a sufficient distance from said beginning so that the housing portions on opposite sides of said groove will be bent with respect to each other during said rupture, but so that no part of said housing will be broken off and propelled from said housing during said rupture.