Relief valve control system for hydraulic dredges

Claim 1

IN THE ASSEMBLY OF A NORMALLY CLOSED RELIEF VALVE ON THE SUCTION PIPE OF A DREDGE, AND MEANS NORMALLY MAINTAINING THE RELIEF VALVE CLOSED BUT OPERATIVE TO QUICKOPEN AND THEREAFTER SLOW-CLOSE THE SAME AND INCLUDING A NORMALLY ENERGIZED SOLENOID AND A CIRCUIT THEREFOR, THE VALVE BEING QUICK-OPENED UPON DEENERGIZATION OF THE SOLENOID AND SLOW-CLOSED UPON REENERGIZATION OF SAID SOLENOID; A DEVICE RESPONSIVE TO AN ABRUPT DROP IN THE PUMPING PRESSURE OF THE DREDGE OPERATIVE TO DEENERGIZE THE SOLENOID AND AFTER A TIME-DELAY TO REENERGIZE THE SAME AND INCLUDING A NORMALLY CLOSED SWITCH INTERPOSED IN THE CIRCUIT, OPPOSED BELLOWS OPERATIVE TO MAINTAIN THE SWITCH CLOSED OR TO OPEN THE SAME UNDER CONDITIONS OF EQUAL OR UNEQUAL PRESSURE RESPECTIVELY IN SAID BELLOWS, AND CONDUITS SUBJECT TO SAID PUMPING PRESSURE AND COUPLED TO CORRESPONDING BELLOWS; THE CONDUIT FOR ONE BELLOWS HAVING A RESTRICTION INTERPOSED THEREIN WHEREBY A DROP IN PUMPING PRESSURE IS REFLECTED IN THE BELLOWS WITH A TIMEDELAY IN ONE RELATIVE TO THE OTHER SO THAT UNEQUAL PRESSURE EXISTS IN SAID BELLOWS, AND THE SWITCH IS OPEN, DURING THE PERIOD OF SAID TIME-DELAY.