Milling machine with hydraulically actuated rotor drive transmission

A propelled milling machine comprising:

• a machine frame supported on a plurality of propulsion components for travel over a work surface,
• an internal combustion engine supported on the machine frame and operatively associated with the plurality of propulsion components for propelling the propelled milling machine;
• a cutting rotor rotatably supported by the machine frame for milling a work surface;
• a rotor drive transmission operatively driven by the internal combustion engine and operatively associated with the cutting rotor to rotate the cutting rotor with respect to the machine frame, the rotor drive transmission including a plurality of gears selectively engageable with each other to adjust rotational speed of the cutting rotor, the plurality of gears including at least a high gear ratio and a low gear ratio;
• a rotor transmission hydraulic circuit in fluid communication with a hydraulic pump to receive hydraulic fluid and with a fluid reservoir to return hydraulic fluid, the rotor transmission hydraulic circuit including a hydraulic gearshift actuator operatively associated with the plurality of gears, a gearshift directional control valve to selectively establish fluid communication between the hydraulic gearshift actuator and one of the hydraulic pump and the fluid reservoir, and a gearshift trapping valve disposed in fluid communication between the hydraulic gearshift actuator and the gearshift directional control valve, the gearshift trapping valve configured to maintain hydraulic pressure in the hydraulic gearshift actuator in occurrence of a fault condition;
• a pressure sensor disposed to measure localized hydraulic pressure;
• and
• an electronic controller in electronic communication with the rotor transmission hydraulic circuit and the pressure sensor, the electronic controller is programmed to use the gearshift trapping valve to maintain hydraulic pressure in the hydraulic gearshift actuator in occurrence of the fault condition, wherein the fault condition is a pressure loss event in the rotor transmission hydraulic circuit, and wherein the electronic controller is programmed to conduct a trapping valve check step to determine whether to de-energize the trapping valve to actuate a poppet check valve to prevent fluid communication between the hydraulic gearshift actuator and the gearshift directional control valve.

A method of operating a rotor drive transmission operatively associated with an electronic controller, the method comprising:

• actuating a gearshift directional control valve to direct pressurized hydraulic fluid from a hydraulic fluid source to a hydraulic gearshift actuator operatively associated with the rotor drive transmission;
• engaging a plurality of gears in the rotor drive transmission to establish a gear ratio of the rotor drive transmission;
• transmitting motive power from an internal combustion engine to a cutting rotor through the rotor drive transmission in the gear ratio;
• and
• actuating a gearshift trapping valve disposed between the gearshift directional control valve and the hydraulic gearshift actuator to maintain hydraulic pressure in the hydraulic gearshift actuator upon occurrence of a fault condition with a rotor transmission hydraulic circuit, the rotor transmission hydraulic circuit including the gearshift directional control valve and the hydraulic gearshift actuator,
• sensing the fault condition with a pressure sensor operatively associated with the rotor drive hydraulic circuit, wherein the fault condition is a hydraulic pressure fault indicating a loss of hydraulic pressure in the rotor transmission hydraulic circuit.

A rotor transmission hydraulic circuit operatively associated with a rotor drive transmission operatively disposed between an internal combustion engine and a cutting rotor, the rotor transmission hydraulic circuit comprising:

• a hydraulic gearshift actuator operatively associated with a plurality of gears in the rotor drive transmission to selectively engage the plurality of gears in one or more gear ratios;
• a gearshift directional control valve to selectively establish fluid communication between the hydraulic gearshift actuator and one of a hydraulic pump and a fluid reservoir;
• and
• a gearshift trapping valve disposed in fluid communication between the hydraulic gearshift actuator and the gearshift directional control valve, the gearshift trapping valve positionable to establish fluid communication between the hydraulic gearshift actuator and the gearshift directional control valve when energized and to maintain hydraulic pressure in the hydraulic gearshift actuator when de-energized upon occurrence of a fault condition,
• a pressure sensor operatively associated with the rotor transmission hydraulic circuit to sense hydraulic pressure therein;
• and
• an electronic controller in electronic communication with the rotor transmission hydraulic circuit and the pressure sensor, and the fault condition is a pressure loss event with the rotor transmission hydraulic circuit as sensed by the pressure sensor.