Hydraulic installation for soil-working implements

Claim 1

IN A HITCH INTERCONNECTING AN AGRICULTURAL IMPLEMENT AND A TRACTOR, IN COMBINATION, TWO GENERALLY ELONGATED LINK MEMBERS ARTICULATED TO SAID IMPLEMENT AND PIVOTALLY CONNECTED TO SAID TRACTOR AT LOCATIONS SPACED ON ABOVE THE OTHER, AT LEAST ONE OF SAID LINK MEMBERS BEING EXTENSIBLE AND PROVIDED WITH A HYDRAULIC CYLINDER AND A DIFFERENTIAL PISTON DISPLACEABLE WITHIN SAID CYLINDER FOR VARYING THE LENGTH OF SAID ONE OF SAID MEMBERS, A SOURCE OF FLUID UNDER PRESSURE OPERATIVELY COUPLED WITH SAID CYLINDER; A FLUID-CONTROL VALVE FOR REGULATING THE PRESSURE APPLIED TO SAID PISTON; MANUALLY OPERABLE REGULTING MEANS FOR ADJUSTING SAID VALVE, SAID REGULATING MEANS INCLUDING A FIRST LEVER MANUALLY DISPLACEABLE ABOUT A SUBSTANTIALLY FIXED FULCRUM RELATIVE TO SAID TRACTOR AND LINK MEANS INTERCONNECTING SAID VALVE AND SAID FIRST LEVER; ANOTHER LEVER HAVING TWO ARMS OF UNEQUAL LENGTH FULCRUMED TO SAID IMPLEMENT; A FEELER WHEEL JOURNALED TO THE LONGER ONE OF SAID ARMS AND ENGAGING THE GROUND; AND TRANSMISSION MEANS INCLUDING A THIRD LEVER ANGULARLY DISPLACEABLE RELATIVE TO SAID FIRST LEVER ABOUT SAID FULCRUM, MEANS FOR RELEASABLY INDEXING SAID FIRST AND THIRD LEVERS IN SELECTED ANGULAR POSITIONS RELATIVE TO EACH OTHER, AN ELONGATED FLEXIBLE MEMBER OPERATIVELY CONNECTING THE OTHER OF SAID ARMS WITH SAID THIRD LEVERS WHEREBY THE LENGTH OF SAID ONE OF SAID MEMBERS IS CONTINUOUSLY VARIED IN RESPONSE TO GROUND-SURFACE VARIATIONS DETECTED BY SAID FEELER WHEEL TO ADJUST CONTINUOUSLY THE POSITION OF SAID IMPLEMENT RELATIVE TO SAID SURFACE.