Stationary hydraulic lifting apparatus

Claim 1

STATIONARY HYDRAULIC LIFTING APPARATUS, PARTICULARLY FOR LIFTING VEHICLES, COMPRISING, IN COMBINATION, A SUBSTANTIALLY VERTICAL PIT OF PREDETERMINED DEPTH AND TRANSVERSE DIMENSIONS; CYLINDRICAL HOUSING MEANS COMPRISING A TUBULAR SHELL OF A DIAMETER SMALLER THAN ANY TRANSVERSE DIMENSION OF SAID PIT, A BOTTOM PLATE AT ITS LOWER END, AND A FLANGE AT ITS UPPER END WHICH RESTS ON THE EDGE OF SAID PIT SO THAT THE ENTIRE HOUSING MEANS IS FREELY SUSPENDED IN SAID PIT; A TUBULAR LIFTING CYLINDER MEANS VERTIALLY MOVABLE WITHIN SAID HOUSING MEANS; GUIDE MEANS FOR SLIDABLY GUIDING AND SAID TUBULAR LIFTING CYLINDER MEANS WITHIN SAID HOUSING MEANS DURING ITS MOVEMENTS; STATIONARY TUBULAR PISTON MEANS WITHIN SAID CYLINDER MEANS AND SUPPORTED BY SAID BOTTOM PLATE, SAID PISTON MEANS BEING NEAR ITS UPPER END OPEN AND INCLUDING SEALING MEANS FOR FLUID-TIGHT SLIDING ENGAGEMENT WITH THE INNER SURFACE OF SAID CYLINDER MEANS; A PLATFORM FOR CARRYING A LOAD AND MOUNTED ON TOP OF SAID CYLINDER MEANS; AND PRESSURE FLUID SUPPLY AND CONTROL MEANS FOR OPERATING SAID MOVABLE LIFTING CYLINDER MEANS AND INCLUDING A SINGLE FLUID DUCT MEANS TERMINATING AT ONE END AT THE BOTTOM END OF SAID PISTON MEANS FOR INTRODUCING FLUID THROUGH SAID PISTON MEANS INTO SAID LIFTING CYLINDER MEANS AND FOR DRAINING IN OPPOSITE DIRECTION SAID FLUID FROM SAID LIFTING CYLINDER MEANS, PRESSURE PUMP MEANS AT THE OTHER END OF SAID DUCT MEANS, MANUALLY OPERABLE RELIEF VALVE MEANS IN PARALLEL WITH SAID PUMP MEANS, A CONTROLLABLE CHECK VALVE MEANS MOUNTED IN SAID DUCT MEANS AT SAID BOTTOM OF SAID HOUSING MEANS FOR PERMITTING SAID FLUID TO BE INTRODUCED UNDER PRESSURE INTO SAID LIFTING CYLINDER MEANS AND FOR AUTOMATICALLY BLOCKING RETURN FLOW THEREOF WHEN NO PRESSURE FLUID IS DELIVERED BY SAID PUMP MEANS, AND CONTROL MEANS FOR CAUSING WHEN DESIRED SAID CHECK VALVE MEANS TO OPEN AND TO PERMIT RETURN FLOW OF SAID FLUID PROVIDED THAT SIMULTANEOUSLY SAID RELIEF VALVE MEANS IS OPENED.