Implement control means for tractor operated agricultural implements

Claim 1

IN A TRACTOR HAVING IMPLEMENT-ATTACHING MECHANISM INCLUDING A PLURALITY OF HITCH LINKS TRAILINGLY PIVOTED ON THE REAR PORTION OF THE TRACTOR AND HAVING MEANS AT THEIR TRAILING ENDS FOR PIVOTAL ATTACHMENT AT VERTICALLY SPACED POINTS TO AN EARTH-WORKING IMPLEMENT AND STRESSED IN DIRECT RELATIONSHIP TO THE DRAFT LOAD THEREON, HYDRAULIC ACTUATOR MEANS MOUNTED ON THE TRACTOR AND CONNECTED TO SAID LINKS FOR RAISING AND LOWERING AN ATTACHED IMPLEMENT, AND ACTUATOR CONTROL VALVE MEANS ACTUABLE FOR CONTROLLING THE OPERATION OF SAID ACTUATOR MEANS, THE COMBINATION COMPRISING: DRAFT-SENSING MEANS INCLUDING HYDRAULIC MOTOR MEANS TELECOPINGLY INTERPOSED EXTERIORLY OF THE TRACTOR IN AT LEAST ONE OF SAID LINKS; DRAFT-SIGNALLING MEANS INCLUDING A HYDRAULIC DISPLACEMENT DEVICE SUPPORTABLY CARRIED BY THE TRACTOR; CONDUIT MEANS INCLUDING A SUPPLY OF HYDRAULIC FLUID THEREIN COMMUNICATIVELY INTERCONNECTING SAID HYDRAULIC MOTOR MEANS AND SAID HYDRAULIC DISPLACEMENT DEVICE; SAID HYDRAULIC MOTOR MEANS BEING TELESCOPINGLY OPERATIVE FOR CREATING PRESSURE DIFFERENTIALS PROPORTIONAL TO THE DRAFT LOAD BETWEEN OPPOSITE ENDS OF SAID HYDRAULIC MOTOR MEANS ATTENDANT DRAFT-PRODUCED CHANGES IN STRESS IN SAID LINKS; SAID HYDRAULIC DISPLACEMENT DEVICE HAVING MEANS THEREIN VARIABLY POSITIONABLE RESPONSIVE TO SAID PRESSURE DIFFERENTIALS; AND MOVEMENT-TRANSMITTING MEANS INTERCONNECTED BETWEEN SAID DRAFT-SIGNALLING MEANS AND SAID ACTUATOR CONTROL VALVE MEANS AND OPERATIVELY RESPONSIVE TO MOVEMENTS OF SAID VARIABLY POSITIONABLE MEANS FOR ACTUATING SAID ACTUATOR CONTROL VALVE MEANS TO EFFECT AN ADJUSTMENT OF THE DEPTH OF THE IMPLEMENT IN THE GROUND AND THEREBY TO MAINTAIN A SUBSTANTIALLY CONSTANT DRAFT THEREON.