Lifting apparatus

Claim 1

A HYDRAULIC LIFTING APPARATUS COMPRISING A BASE; A PLURALITY OF MOVING PARTS INCLUDING A PLATFORM LOCATED ABOVE AND MOVABLE TOWARD AND AWAY FROM SAID BASE, AND SUPPORTING MEANS OPERATIVELY CONNECTED WITH SAID BASE AND WITH SAID PLATFORM AND ARRANGED TO MOVE THE PLATFORM BETWEEN AN UPPER AND A LOWER END POSITIONS; OPERATING MEANS ARRANGED TO MOVE SAID SUPPORTING MEANS AND INCLUDING A SOURCE OF HYDRAULIC FLUID, A HYDRAULIC LIFTING DEVICE, A SUPPLY CONDUIT CONNECTING SAID SOURCE WITH SAID LIFTING DEVICE, AND PUMP MEANS MOUNTED IN SAID SUPPLY CONDUIT TO DELIVER FLUID TO SAID LIFTING DEVICE WHEREBY THE LATTER ACTS UPON ONE OF SAID MOVING PARTS AND MOVES THE PLATFORM TO SAID UPPER END POSITION; A FIRST RETURN CONDUIT CONNECTED WITH SAID SUPPLY CONDUIT DOWNSTREAM OF SAID PUMP MEANS AND ARRANGED TO RETURN PRESSURE FLUID TO SAID SOURCE; A NORMALLY CLOSED MULTIWAY VALVE IN SAID RETURN CONDUIT; A SECOND RETURN CONDUIT CONNECTING SAID MULITWAY VALVE WITH SAID SOURCE; A FIRST MOVABLE OPENER OPERATIVELY CONNECTED WITH AND ARRANGED TO OPEN IN SAID MULTIWAY VALVE A PASSAGE FOR THE FLOW OF PRESSURE FLUID FROM SAID FIRST RETURN CONDUIT TO SAID SECOND RETURN CONDUIT IN RESPONSE TO MOVEMENT THEREOF: A SECOND MOVABLE OPENER OPERATIVELY CONNECTED WITH SAID MULTIWAY VALVE AND ARRANGED TO PERMIT FLOW OF FLUID THROUGH SAID FIRST RETURN CONDUIT IN RESPONSE TO MOVEMENT THEREOF; A PRESSURE RELIEF VALVE MOUNTED IN SAID FIRST RETURN CONDUIT DOWNSTREAM OF SAID MULTIWAY VALVE FIRST ACTUATING MEANS CONNECTED WITH ONE OF SAID MOVABLE PARTS AND ARRANGED TO MOVE SAID SECOND OPENER IN RESPONSE TO MOVEMENT OF SAID PLATFORM TO AN INTERMEDIATE POSITION BETWEEN SAID END POSITIONS SO THAT SAID SECOND OPENER PERMITS THE FLOW OF FLUID TO SAID PRESSURE RELIEF VALVE WHEN THE PUMP MEANS IS IN OPERATION; AND SECOND ACTUATING MEANS CONNECTED WITH ONE OF SAID MOVING PARTS AND ARRANGED TO MOVE SAID FIRST OPENER WHEN THE PLATFORM AT LEAST APPROACHES SAID UPPER END POSITION SO THAT SAID MULTIWAY VALVE PERMITS ANY ADDITIONAL FLUID DELIVERED BY SAID PUMP MEANS TO FLOW THROUGH SAID SECOND RETURN CONDUIT AND BACK TO SAID SOURCE.