Hydrostatic Circuit Flushing Flow Cancellation

A hydrostatic circuit comprising:

• a hydrostatic pump connected to first and second input/output lines;
• the first and second input/output lines connected to a hydrostatic motor to form a loop;
• the first and second input/output lines also connected to a flush valve, the flush valve including a spool that is moveable between a first position providing communication between the first input/output line and a flush outlet line, a second position providing communication between the second input/output line and the flush outlet line and a third position wherein the flush valve isolates the first and second input/output lines from the flush outlet line;
• the flush outlet line terminating at a flush outlet;
• a controller linked to at least one flush valve override component selected from the group consisting of
• a normally open solenoid control valve disposed downstream of the flush valve and upstream of the flush outlet and in communication with the controller and being moveable to a closed position for stopping flow from the flush valve to the flush outlet,
• a normally open solenoid control valve disposed upstream of the flush valve and in communication with the controller and being moveable to a closed position for stopping flow from the first and second input/output lines to the flush valve,
• a normally open solenoid control valve disposed upstream of the flush valve and in communication with the controller and being moveable to a closed position for preventing communication between the first and second input/output lines and the flush valve, and
• a pair of solenoids disposed at opposing ends of the flush valve and in communication with the controller for maintaining the flush valve in its normally closed position;
• and
• at least one temperature sensor linked to the controller for communicating a temperature of fluid in the hydrostatic circuit to the controller, and
• a plurality of pressure sensors linked to the controller for communicating pressures in the first and second input/output lines to the controller.

A method for overriding a flushing function of a flush valve of a closed loop hydrostatic circuit, the method comprising:

• overriding the flushing function in response to at least one operating condition selected from the group consisting of:
• a) measuring a temperature of a fluid in the circuit,
• if the temperature of the fluid is below a predetermined minimum temperature, sending a signal to stop any flushing flow from the circuit to a flush outlet,
• b) measuring a loop pressure of the fluid in the circuit,
• if the loop pressure is below a predetermined minimum loop pressure, sending a signal to stop any flushing flow from the circuit to the flush outlet,
• c) measuring pressures in first and second input/output lines of the circuit,
• calculating a difference (ΔP) between the pressures in the first and second input/output lines,
• if the ΔP is below a predetermined minimum ΔP, sending a signal to stop any flushing flow from the circuit to the flush outlet,
• d) receiving a turning command,
• sending a signal to stop any flushing flow from the circuit to the flush outlet,
• e) receiving a turning command,
• sending a signal to stop any flushing flow from the circuit to the flush outlet,
• timing a duration of the turning command,
• if the duration of the turning command exceeds a predetermined maximum turning time period, sending a signal to initiate flushing flow from the circuit to the flush outlet,
• receiving a straight steering command,
• sending a signal to initiate flushing flow from the circuit to the flush outlet.