Hydraulic power unit and control system for tractors

Claim 1

IN A POWER OPERATING SYSTEM FOR A TRACTOR IMPLEMENT HITCH LINKAGE, THE COMBINATION OF A HYDRAULIC ACTUATOR MOUNTED ON THE TRACTOR AND CONNECTED TO THE LINKAGE FOR RAISING AND LOWERING IT, A CONTINUOUSLY RUNNING PUMP SUPPLYING PRESSURE FLUID FOR THE OPERATION OF SAID ACTUATOR, VALVE MEANS CARRIED BY THE TRACTOR CONTROLLING THE SUPPLY OF PRESSURE FLUID TO AND EXHAUST OF PRESSURE FLUID FROM SAID ACTUATOR, A BY-PASS VALVE INTERPOSED BETWEEN SAID PUMP AND SAID VALVE MEANS OPERATIVE WHEN OPENED TO DIRECT THE PUMP OUTPUT TO EXHAUST, DRAFT LOAD RESPONSIVE CONTROL MEANS FOR SAID VALVE MEANS, POSITION RESPONSIVE CONTROL MEANS FOR SAID VALVE MEANS, A CONTROL SHAFT ADAPTED TO BE ROCKED THROUGH POSITION CONTROL AND DRAFT CONTROL RANGES DISPOSED AT OPPOSITE SIDES OF AN INTERMEDIATE RANGE, MEANS OPERABLE BY SAID SHAFT WHEN IN SAID INTERMEDIATE RANGE ACTING TO DISABLE BOTH SAID DRAFT LOAD RESPONSIVE AND SAID POSITION RESPONSIVE CONTROL MEANS AND BEING OPERATIVE TO CONDITION SAID CONTROL MEANS FOR OPERATION RESPECTIVELY WHEN SAID SHAFT IS ROCKED TO THE DRAFT CONTROL AND POSITIONAL CONTROL RANGES, MEANS OPERATED IN ACCORDANCE WITH THE POSITION OF THE HITCH LINKAGE FOR OPENING SAID BY-PASS VALVE WHEN SAID SHAFT IS ROCKED TO THE LIMIT OF EITHER CONTROL RANGE ADJACENT ONE END OF SAID INTERMEDIATE RANGE, AND MEANS CARRIED BY SAID SHAFT OPERATIVE TO CLOSE SAID BY-PASS VALVE AS THE SHAFT IS ROCKED TO A PREDETERMINED POSITION WITHIN SAID INTERMEDIATE RANGE.