Fail-safe gate-operating apparatus

Claim 1

FAIL-SAFE GATE-OPERATING APPARATUS COMPRISING A FLUID PRESSURE CYLINDER, A PISTON THEREIN, A PISTON ROD ATTACHED TO THE PISTON AND EXTENDING OUT OF ONE END OF THE CYLINDER FOR OPENING AND CLOSING A GATE, PIPES CONNECTED TO THE OPPOSITE ENDS OF THE CYLINDER, A SOURCE OF COMPRESSED AIR, CONTROL MEANS FOR SELECTIVELY CONNECTING SAID SOURCE WITH EITHER OF SAID PIPES AND CONNECTING THE OTHER PIPE WITH THE ATMOSPHERE TO MOVE THE PISTON FROM ONE END OF THE CYLINDER TO THE OTHER, A NORMALLY CLOSED FIRST VALVE IN THE PIPE THAT DELIVERS COMPRESSED AIR TO THE END OF THE CYLINDER FROM WHICH THE PISTON MOVES TO CLOSE THE GATE, SAID VALVE CONTAINING FLUID PRESSURE RESPONSIVE MEANS FOR OPENING IT, MEANS FOR DELIVERING COMPRESSED AIR FROM SAID SOURCE TO SAID PRESSURE RESPONSIVE MEANS TO HOLD THE VALVE OPEN DURING NORMAL OPRATION OF THE APPARATUS IS RESERVOIR CONTAINING COMPRESSED AIR WHILE THE APPARATUS IS OPERATING NORMALLY, A CONDUIT CONNECTING THE RESERVOIR WITH SAID VALVED PIPE BETWEEN SAID VALVE AND CYLINDER, A NORMALLY OPEN SECOND VALVE IN SAID CONDUIT PROVIDED WITH FLUID PRESSURE RESPONSIVE MEANS FOR CLOSING IT, MEANS FOR DELIVERY COMPRESSED AIR FROM SAID SOURCE TO THE PRESSURE RESPONSIVE MEANS OF THE SECOND VALVE TO HOLD THAT VALVE CLOSED DURING NORMAL OPERATION OF THE APPARATUS, A PREDETERMINED REDUCTION IN THE AIR PRESSURE AT SAID SOURCE OR BETWEEN IT AND SAID FIRST VALVE PERMITTING THE FIRST VALVE TO CLOSE AND SAID SECOND VALVE TO OPEN SO THAT COMPRESSED AIR FROM THE RESERVOIR CAN REVERSE THE PISTON.