Piston for gas storage tank

Claim 1

IN AN UPSTANDING SUBSTANTIALLY CYLINDRICAL TANK FOR STORING GAS UNDER PRESSURE, THE VERTICALLY MOVABLE PISTON COMBINATION COMPRISING A SUBSTANTIALLY CIRCULAR SEMIFLEXIBLE METAL DIAPHRAGM SIDPOSED WITHIN THE TANK AND ADAPTED TO REST BY GRAVITY UPON THE BODY OF GAS CONTAINED THEREIN AND ARRANGED FOR FREE VERTICAL MOVEMENTS WITHIN THE TANK UPON INCREASE AND DECREASE OF THE VOLUME OF THE BODY OF GAS, SEALING MEANS ABOUT THE PERIPHERY OF SAID DIAPHRAGM COOPERATING WITH THE UPRIGHT CYLINDRICAL SIDE WALL OF THE TANK TO PREVENT LEAKAGE OF THE GAS BETWEEN THE PERIPHERY OF SAID DIAPHRAGM AND THE WALL OF THE TANK, A RIGID UPSTANDING CONCRETE ANNULUS OF SUBSTANTIAL, WEIGHT SUPPORTED CONCENTRICALLY UPON THE UPPER SIDE OF SAID DIAPHRAGM TO INCREASE THE GRAVITATIONAL FORCES ACTING UPON SAID DIAPHRAGM AND THEREBY INCREASE THE PRESSURE OF THE GAS, SAID ANNULUS DIVIDING SAID DIAPHRAGM INTO CENTRAL PORTION ENCOMPASSED BY SAID ANNULUS AND AN ANNULAR PERIPHERAL PORTION EXTENDING RADIALLY OUTWARDLY FROM SAID ANNULUS, MEANS FOR TRANSMITTING TO SAID ANNULUS THE UPWARDLY FLEXING FORCES EXERTED UPON SAID PERIPHERAL PORTION OF SAID DIAPHRAGM BY THE GAS DISPOSED THEREBELOW SO AS TO PRODUCE A FIRST TORSIONAL MOMENT IN A FIRST DIRECTION ABOUT SAID ANNULUS, AND MEANS FOR TRANSMITTING TO SAID ANNULUS THE UPWARDLY FLEXING FORCES EXERTED UPON SAID CENTRAL PORTION OF SAID DIAPHRAGM BY THE GAS DISPOSED THEREBELOW SO AS TO PRODUCE A SECOND TORSIONAL MOMENT IN A SECOND DIRECTION ABOUT SAID ANNULUS, SAID FIRST AND SECOND DIRECTIONS BEING OPPOSITE TO EACH OTHER AND SAID FIRST AND SECOND TORSIONAL MOMENTS BEING SUBSTANTIALLY EQUAL, WHERBY SAID TORSIONAL MOMENTS TEND TO BALANCE AND TO COUNTERACT EACH OTHER SO AS TO MINIMIZE THE NET RESULTING TORSIONAL STRESSES IN SAID ANNULUS.