Vent for fuel storage tanks

Claim 1

A RELIEF VALVE COMPRISING A CASING DIVIDED INTO A FIRST HALF AND A SECOND HALF, SAID FIRST HALF HAVING A BACK WALL AND CONTINUOUS SIDE WALLS JOINED THERETO, THE SIDE WALLS TERMINATING IN AN ENCIRCLING OUTWARDLY PROJECTING FLANGE, SAID SECOND HALF HAVING A FORWARD WALL AND CONTINUOUS SIDE WALLS JOINED THERETO, THE SIDE WALLS OF THE SECOND HALF TERMINATING IN AN ENCIRCLING OUTWARDLY PROJECTING FLANGE, SAID FLANGES BEING IN OPPOSING RELATIONSHIP, A NORMALLY FLAT DIAPHRAGM OF RELATIVELY THIN ELASTIC MATERIAL INTERPOSED BETWEEN SAID FIRST AND SECOND HALVES OF THE CASING AND HAVING A PERIPHERAL PORTION TIGHTLY SECURED BETWEEN SAID FLANGES AND DIVIDING THE CASING INTO A FIRST AND A SECOND CHAMBER, THE DIAPHRAGM HAVING PERFORATIONS THERETHROUGH WHICH ARE CLOSED WHEN THE DIAPHRAGM IS IN THE SAID NORMALLY FLAT AND UNSTRETCHED CONDITION, A TUBULAR BODY JOINED AT ONE END TO A SIDE WALL OF SAID FIRST HALF AND OPENING INTO SAID FIRST CHAMBER, SAID FRONT WALL OF SAID SECOND CHAMBER BEING PERFORATED, TWO RELATIVELY CLOSELY SPACED OVERLAPPING PLATES LOCATED IN THE SAID SECOND HALF OF THE CASING BETWEEN THE FRONT WALL OF SAID SECOND CHAMBER AND SAID DIAPHRAGM, SAID SIDE WALL OF THE SECOND HALF HAVING A DRAIN OPENING THEREIN, AND SAID DIAPHRAGM PERFORATIONS BEING OPENED TO PASS FLUID UPON STRETCHING AND BOWING OF THE DIAPHRAGM INTO EITHER OF SAID CHAMBERS RESULTING FROM UNEQUAL FLUID PRESSURES IN THE TWO CHAMBERS.