Tractor with means to effect zero turning radius

Claim 1

A VEHICLE HAVING AN ELONGATED CHASSIS, FRONT AND REAR AXLES, WHEELS MOUNTED ON THE REAR AXLE FOR ROTATION ABOUT THE AXIS THEREOF, WHEELS MOUNTED ON THE FRONT AXLE FOR ROTATION ABOUT THE AXIS THEREOF AND FOR MOVEMENT ABOUT VERTICALLY EXTENDING AXES, AND MEANS TO MOVE THE FRONT WHEELS ABOUT SAID VERTICALLY EXTENDING AXES INTO POSITIONS DIVERGING OUTWARDLY OF THE CHASSIS WHEREBY THE VEHICLE MAY BE TURNED ABOUT THE INTERSECTION OF THE LONGITUDINAL AXIS OF THE CHASSIS AND THAT OF THE REAR AXLE TO PROVIDE A ZERO TURNING RADIUS, SAID MEANS INCLUDING AN HYDRAULIC PUMP, A PAIR OF CYLINDERS OPERATIVELY CONNECTED TO EACH OTHER AND TO SAID PUMP, PISTON RODS SLIDABLE IN SAID CYLINDERS HAVING INNER ENDS DISPOSED IN SAID CYLINDERS AND OUTER ENDS PIVOTALLY ATTACHED TO THE FRONT WHEELS, AND A VALVE TO ADMIT FLUID INTO SAID CYLINDERS SELECTIVELY TO ONE SIDE AND THE OTHER OF THE INNER ENDS OF SAID PISTON RODS TO THEREBY SELECTIVELY EXTEND SAID PISTON RODS AND CAUSE THE FRONT WHEELS TO MOVE ABOUT SAID VERTICALLY EXTENDING AXES TO DIVERGENT POSITIONS AND RETRACT SAID PISTON RODS AND CAUSE THE FRONT WHEELS TO RETURN TO THEIR ORIGINAL POSITIONS, MEANS TO MOVE THE FRONT WHEELS ABOUT SAID VERTICALLY EXTENDING AXES INTO POSITIONS OF SUBSTANTIAL PARALLELISM, AND MEANS TO STEER THE FRONT WHEELS WHILE IN SAID POSITIONS OF SUBSTANTIAL PARALLELISM INCLUDING A POWER STEERING UNIT, A SECOND HYDRAULIC CYLINDER MOUNTED ON SAID CHASSIS HAVING A SECOND PISTON ROD SLIDABLE THEREIN, AND