Hydraulic propulsion drive mechanism

Claim 1

IN AN AGRICULTURAL COMBINE VEHICLE HAVING AN OPERATOR''S STATION, A PAIR OF LATERALLY SPACED-APART MAIN TRACTION WHEELS SUPPORTABLY MOUNTED AT ONE END OF THE VEHICLE, AND A PAIR OF LATERALLY SPACED-APART STEERABLE GUIDE WHEELS SUPPORTABLY MOUNTED AT THE OTHER END OF THE VEHICLE, A FOUR-WHEEL DRIVE COMBINATION, COMPRISING: A PLURALITY OF CHANGE-SPEED TRANSMISSIONS OPERATIVELY CONNECTED TO AND MOUNTED IN PART AT LEAST ONE WITHIN EACH WHEEL; A PLURALITY OF FLUID PRESSURE DRIVE MOTORS MOUNTED ON AND OPERATIVELY CONNECTED ONE* TO EACH OF SAID TRANSMISSIONS FOR DRIVING THE ASSOCIATED WHEEL; A FLUID PRESSURE SOURCE; FLUID CONDUIT MEANS INTERCONNECTING SAID FLUID PRESSURE DRIVE MOTORS WITH SAID FLUID PRESSURE SOURCE AND INCLUDING DIRECTIONAL FLOW CONTROL VALVES FOR ALL SAID MOTORS; EACH OF SAID CHANGE-SPEED TRANSMISSIONS ASSOCIATED WITH A MAIN TRACTION WHEEL BEING CONDITIONABLE FOR A PLURALITY OF SPEED RATIO POSITIONS PLUS A NEUTRAL POSITION, AND EACH OF SAID CHANGE-SPEED TRANSMISSIONS ASSOCIATED WITH A GUIDE WHEEL BEING CONDITIONABLE FOR ONE LESS PLURALITY FROM THAT OF SAID MAIN WHEEL TRANSMISSIONS OF SPEED RATIO POSITIONS PLUS A NEUTRAL POSITION; AND HAVING THE RELATIONSHIP OF THE TORQUE-TRANSMITTING CAPACITIES OF THE TRANSMISSIONS OF THE MAIN WHEELS AND GUIDE WHEELS IN THE VARIOUS SPEED RATIOS OF EACH THEREOF ARRANGED SO THAT NORMALLY PROPULSION OF THE VEHICLE IS EFFECTED SOLELY THROUGH THE MAIN WHEELS WHILE THE GUIDE WHEELS PROVIDE NO PROPULSIVE FORCE THEREFOR, BUT FURTHER HAVING SAID GUIDE WHEELS WHILE SAID MAIN TRANSMISSIONS ARE IN CERTAIN OF THE SELECTED SPEED RATIO POSITIONS THEREOF OPERATIVE FOR PROVIDING WHEN ONE OR MORE OF THE MAIN WHEELS SLIP WITH A CONSEQUENT REDUCTION OF TRACTION THEREOF LIMITED PROPULSIVE FORCE FOR AIDING IN PROPELLING THE VEHICLE.