Control system for hydrostatic transmissions

Claim 1

IN A CONTROL ARRANGEMENT FOR A HYDROSTATIC TRANSMISSION HAVING AN INPUT SHAFT ADAPTED TO BE DRIVEN AT VARIABLE SPEED AND ALSO HAVING AN OUTPUT SHAFT: A FLUID PUMP DRIVINGLY CONNECTED TO SAID INPUT SHAFT SO AS TO BE DRIVABLE THEREBY, A FLUID MOTOR DRIVINGLY CONNECTED TO SAID OUTPUT SHAFT FOR DRIVING THE SAME, PRESSURE AND RETURN CONDUITS CONNECTING SAID PUMP WITH SAID MOTOR FOR THE EXCHANGE OF FLUID THEREBETWEEN FOR DRIVING SAID MOTOR WHILE SAID PUMP IS DELIVERING FLUID, A BYPASS VALVE ARRANGED IN PARALLEL TO SAID CONDUITS AND COMPRISING A VALVE MEMBER MOVABLE INTO A FIRST POSITION FOR ESTABLISHING A BYPASS BETWEEN SAID CONDUITS TO PERMIT FLUID IN SAID CONDUITS TO BYPASS SAID MOTOR, SAID VALVE MEMBER ALSO BEING MOVABLE INTO A SECOND POSITION FOR INTERRUPTING SAID BYPASS, SAID VALVE MEMBER ALSO BEING MOVABLE INTO POSITIONS INTERMEDIATE SAID FIRST AND SECOND POSITIONS FOR THROTTLING SAID BYPASS, SPRING MEANS URGING SAID VALVE MEMBER TOWARD SAID FIRST POSITION, SAID VALVE MEMBER HAVING OPERATIVELY ASSOCIATED THEREWITH A FIRST FLUID OPERABLE AREA FOR COMMUNICATION WITH SAID PRESSURE CONDUIT WHICH AREA WHEN SUBJECTED TO FLUID PRESSURE IN SAID PRESSURE CONDUIT ACTS UPON SAID VALVE MEMBER IN THE SAME DIRECTION AS SAID SPRING MEANS, SAID VALVE MEMBER ALSO HAVING OPERATIVELY ASSOCIATED THEREWITH A SECOND FLUID OPERABLE AREA ADAPTED TO BE SUBJECTED TO FLUID PRESSURE FOR ACTING UPON SAID VALVE MEMBER IN A DIRECTION OPPOSITE TO THE DIRECTION OF ACTION OF SAID FIRST FLUID OPERABLE AREA, A SOURCE OF CONTROL FLUID PRESSURE FOR CONVEYING FLUID PRESSURE TO SAID SECOND FLUID OPERABLE AREA, AND SPEED RESPONSIVE MEANS DRIVINGLY CONNECTED TO SAID INPUT SHAFT FOR VARYING THE PRESSURE OF SAID SOURCE OF CONTROL FLUID PRESSURE WITH THE VARYING SPEED OF SAID INPUT SHAFT.