Hydraulically actuated dock board with hinged lip

Claim 1

IN A HYDRAULICALLY OPERATED DOCK BOARD INCLUDING A FRAME MEANS, A RAMP HAVING ONE END PIVOTALLY ATTACHED TO SAID FRAME MEANS, A LIP PIVOTALLY ATTACHED TO THE OTHER END OF SAID RAMP, AND MECHANICAL LINKAGE MEANS DISPOSED BENEATH SAID RAMP AND BEING OPERATIVE TO RAISE AND LOWER SAID RAMP, THE IMPROVEMENT COMPRISING: A FIRST CYLINDER AND PISTON MEANS MOUNTED ON SAID FRAME MEANS AND COUPLED TO SAID MEHANICAL LINKAGE MEANS FOR OPERATION THEREOF; A SECOND CYLINDER AND PISTON MEANS MOUNTED ON THE UNDERSIDE OF SAID RAMP AND COUPLED TO SAID LIP FOR RAISING AND LOWERING THEREOF; A SUPPLY MEANS ADAPTED TO SUPPLY A SOURCE OF ACTUATING FLUID TO SAID FIRST AND SECOND CYLINDER AND PISTON MEANS; A SWITCH MEANS CONTROLLING SAID SUPPLY MEANS FOR SELECTIVE OPERATION THEREOF TO THUS SELECTIVELY SUPPLY ACTUATING FLUID TO SAID FIRST AND SECOND CYLINDER AND PISTON MEANS; CONTROL VALVE MEANS FOR DIRECTING DELIVERY OF SAID ACTUATING FLUID TO A SELECTED CYLINDER AND PISTON MEANS; AND OPERATING MEANS RESPONSIVE TO SAID MECHANICAL LINKAGE MEANS FOR SELECTIVELY ACTUATING SAID CONTROL VALVE MEANS AND THUS DETERMINING TO WHICH CYLINDER AND PISTON MEANS SAID ACTUATING FLUID WILL BE DELIVERED; SAID SWITCH MEANS BEING ACTUATABLE TO OPERATE SAID SUPPLY MEANS AND THUS SUPPLY ACTUATING FLUID FROM SAID SOURCE TO SAID CONTROL VALVE MEANS, WHICH, WHEN ENGAGED BY SAID OPERATING MEANS CAUSES SAID RAMP AND SAID LIP TO RAISE; SAID SWITCH MEANS ALSO BEING DEACTUATABLE TO TERMINATE OPERATION OF SAID SUPPLY MEANS AND TO INTERRUPT THE SUPPLY OF ACTUATING FLUID FROM SAID SOURCE TO SAID CONTROL VALVE MEANS, WHICH, WHEN DISENGAGED BY SAID OPERATING MEANS, CAUSES SAID RAMP AND SAID LIP TO LOWER.