Fluid-operated ramp having automatic lip

Claim 1

A FLUID-OPERATED RAMP FOR BRIDGING THE SPACE BETWEEN A LOADING DOCK AND A VEHICLE BED COMPRISING A PLATFORM, COUPLING MEANS CONNECTING SAID PLATFORM TO SAID LOADING DOCK FOR MOVEMENT BETWEEN EXTERNALLY UNSUPPORTED AND SUPPORTED POSITOIONS, FLUID-OPERATED ELEVATING MEANS CONNECTED TO REACT BETWEEN SAID PLATFORM AND SAID LOADING DOCK FOR RAISING SAID PLATFORM UPWARDLY ABOUT SAID COUPLING MEANS TO A PREDETERMINED INCLINED POSITION, A LIP HINGED TO THE FRONT OF SAID PLATFORM, FLUID-OPERATED LIP ACTUATING MEANS CONNECTED TO REACT BETWEEN SAID LIP AND SAID PLATFORM FOR RAISING SAID LIP FROM A VERTICAL RETRACTED POSITION TO A BRIDGING POSITION IN WHICH IT FORMS A CONTINUATION OF SAID PLATFORM, A SOURCE OF FLUID PRESSURE, A FLUID SYSTEM CONNECTING SAID SOURCE OF FLUID PRESSURE TO SAID FLUID-OPERATED ELEVATING MEANS AND SAID FLUIDOPERATED LIP ACTUATING MEANS, RESTRAINING MEANS IN SAID ELEVATING MEANS WHEREBY THE PRESSURE IN SAID FLUID SYSTEM IS RAISED TO A PREDETERMINED PEAK OPERATING PRESSURE WHEN SAID PLATFORM IS RAISED TO SAID PREDETERMINED INCLINED PORTION, RESTRICTING MEANS IN SAID FLUID SYSTEM FOR MAINTAINING THE PRESSURE IN SAID SYSTEM ABOVE A PREDETERMINED LOWER PRESSURE DURING A PERIOD WHEN THE PLATFORM MOVES FROM SAID UNSUPPORTED TO A SUPPORTED POSITION, A MULTI-STAGE VALVE MEANS IN SAID FLUID SYSTEM FOR CONTROLLING THE APPLICATION AND DRAINING OF PRESSURE TO AND FROM SAID FLUID-OPERATED LIP ACTUATING MEANS, SAID VALVE MEANS HAVING A DRAINING CONDITION WHICH CAUSES PRESSURE TO BE DRAINED FROM SAID FLUID-OPERATED LIP ACTUATING MEANS, AND A PRESSURE-APPLYING CONDITION WHICH CAUSES PRESSURE TO BE APPLIED TO SAID FLUID-OPERATED LIP ACTUATING MEANS, SAID VALVE MEANS INCLUDING A VALVE SECTION AND AN OPERATING SECTION EACH HAVING DRAINING AND PRESSURE-APPLYING POSITIONS, SAID OPERATING SECTION HAVING A CHAMBER, CONDUIT MEANS CONNECTING SAID CHAMBER TO SAID FLUID SYSTEM, A MOVABLE VALVE OPERATOR IN SAID CHAMBER HAVING DRAINING AND PRESSURE APPLYING POSITIONS, BIASING MEANS URGING SAID VALVE MEANS TO SAID DRAINING CONDITION, SAID VALVE OPERATOR INCLUDING RELATIVELY SMALLER AND LARGER PRESSURE RESPONSIVE CONTROL SURFACES FOR CONTROLLING THE MOVEMENT OF SAID OPERATOR, GATE MEANS IN SAID CHAMBER CONFINING THE FLUID PRESSURE IN SAID FLUID SYSTEM TO SAID RELATIVELY SMALLER CONTROL SURFACE WHEN SAID VALVE MEANS IS IN SAID DRAINING CONDITION AND TO SAID RELATIVELY LARGER CONTROL SURFACE WHEN SAID VALVE MEANS IS IN SAID PRESSURE-APPLYING CONDITION, THE FORCE APPLIED BY SAID BIASING MEANS BEING GREATER THAN THE OPPOSING FORCE ON SAID SMALLER SURFACE PRODUCED WHEN THE PRESSURE IN SAID FLUID SYSTEM IS BELOW SAID PREDETERMINED PEAL WHEREBY SAID VALVE MEANS IS CAUSED TO REMAIN IN SAID DRAINING CONDITION WHILE SAID PLATFORM IS BELOW SAID PREDETERMINED INCLINED POSITION, THE FORCE APPLIED BY SAID BIASING MEANS BEING LESS THAN THE OPPOSING FORCE ON SAID SMALLER SURFACE OVERCOMES THE PRESSURE IN SAID FLUID SYSTEM IS AT SAID PREDETERMINED PEAK WHEREBY THE FORCE OF SAID SMALLER SURFACE OVERCOMES SAID BIASING MEANS AND SAID VALVE MEANS IS CAUSED TO MOVE TO SAID PRESSURE-APPLYING CONDITION WHEN SAID PLATFORM IS RAISED TO SAID PREDETERMINED INCLINED POSITION, THE FORCE APPLIED BY SAID BIASING MEANS BEING LESS THAN THE FORCE ON SAID LARGER SURFACE PRODUCED WHEN THE PRESSURE IN SAID FLUID SYSTEM IS ABOVE SAID PREDETERMINED LOWER PRESSURE WHEREBY SAID VALVE MEANS IS CAUSED TO REMAIN IN SAID PRESSURE-APPLYING CONDITION FOR A PERIOD WHILE SAID PLATFORM REMAINS EXTERNALLY UNSUPPORTED, AND THE FORCE APPLIED BY SAID BIASING MEANS BEING GREATER THAN THE OPPOSING FORCE PRODUCED WHEN THE PRESSURE IN SAID FLUID SYSTEM DROPS BELOW SAID PREDETERMINED LOWER PRESSURE WHEREBY SAID VALVE MEANS IS CAUSED TO MOVE TO SAID DRAINING POSITION AFTER SAID PLATFORM BECOMES EXTERNALLY SUPPORTED.