Harvester row unit height control with electrohydraulic proportional valve structure

A harvester having a frame adapted for forward movement over a field and including a row unit supported for vertical movement relative to the frame by a hydraulic lift assembly, the harvester including height control structure for controlling the lift assembly comprising:

• a ground sensor providing a height signal dependent on the position of the row unit relative to the surface of the ground;
• a first proportional valve connected to a source of hydraulic pressure on the harvester and to the lift assembly;
• an electronic controller connected to the first proportional valve and to the ground sensor, the controller responsive to the height signal for providing an electrical valve control signal to the first proportional valve to operate the lift assembly and maintain a preselected vertical position of the row unit relative to the ground in an automatic mode, wherein the valve control signal is dependent on the difference between the preselected vertical position and actual row unit position relative to the ground;
• an electrohydraulic valve connected to the controller and the lift assembly and having an on position for providing lift assembly operation for lowering the row unit and a closed position for preventing lowering of the row unit;
• a second proportional valve connected between the lift assembly and a return line to the source of hydraulic pressure, the controller providing simultaneous control of the proportional valves to effect raising and lowering of the lift assembly;
• wherein the second proportional valve is connected in series with the electrohydraulic valve to prevent unwanted lowering of the lift assembly when the harvester is not operating in the automatic mode;
• and
• wherein the controller includes an input receiving a row unit status device signal and provides a signal to the electrohydraulic valve for moving the electrohydraulic valve to the closed position when the row unit status device signal indicates the unit is not operating.

A harvester having a frame adapted for forward movement over a field and including a row unit supported for vertical movement relative to the frame by a hydraulic lift assembly, the harvester including height control structure for controlling the lift assembly comprising:

• a ground sensor providing a height signal dependent on the position of the row unit relative to the surface of the ground;
• a first proportional valve connected to a source of hydraulic pressure on the harvester and to the lift assembly;
• an electronic controller connected to the first proportional valve and to the ground sensor, the controller responsive to the height signal for providing an electrical valve control signal to the first proportional valve to operate the lift assembly and maintain a preselected vertical position of the row unit relative to the ground in an automatic mode, wherein the valve control signal is dependent on the difference between the preselected vertical position and actual row unit position relative to the ground;
• an electrohydraulic valve connected to the controller and the lift assembly and having an on position for providing lift assembly operation for lowering the row unit and a closed position for preventing lowering of the row unit;
• wherein the hydraulic lift assembly comprises a single acting cylinder having a base end connected through the first proportional valve to a hydraulic pressure line, the base end also connected through a second proportional valve to a hydraulic return line, the controller simultaneously controlling the first and second proportional valves to raise and lower the row unit;
• and
• wherein the controller is responsive to a row unit enabled signal and prevents operation in the automatic mode when the row unit is not enabled.

A harvester having a frame adapted for forward movement over a field and including a row unit supported for vertical movement relative to the frame by a hydraulic lift assembly, height control structure for controlling the lift assembly comprising:

• a ground sensor providing a height signal dependent on the position of the row unit relative to the surface of the ground;
• electrohydraulic proportional valve structure connected to a source of hydraulic pressure on the harvester and to the lift assembly;
• an electronic controller connected to the proportional valve structure and to the ground sensor, the controller responsive to the height signal for providing an electrical valve control signal to the proportional valve structure to operate the lift assembly and maintain a preselected vertical position of the row unit relative to the ground, wherein the control valve signal is dependent on the difference between the preselected vertical position and actual row unit position relative to the ground;
• wherein the controller includes an adjustment for varying the control valve signal for a given height signal to adjust rate of response of the lift assembly;
• and
• wherein the ground sensor comprises a transducer located on the row unit, and further comprising means for adjusting the position of at least a portion of the transducer from a location remote from the row unit to vary the output of the ground sensor for a given position of the row unit relative to the surface of the ground.

A harvester having a frame adapted for forward movement over a field and including a row unit supported for vertical movement relative to the frame by a hydraulic lift assembly, height control structure for controlling the lift assembly comprising:

• a ground sensor providing a height signal dependent on the position of the row unit relative to the surface of the ground;
• electrohydraulic proportional valve structure connected to a source of hydraulic pressure on the harvester and to the lift assembly;
• an electronic controller connected to the proportional valve structure and to the ground sensor, the controller responsive to the height signal for providing an electrical valve control signal to the proportional valve structure to operate the lift assembly and maintain a preselected vertical position of the row unit relative to the ground, wherein the control valve signal is dependent on the difference between the preselected vertical position and actual row unit position relative to the ground;
• wherein the controller includes an adjustment for varying the control valve signal for a given height signal to adjust rate of response of the lift assembly;
• and
• wherein the controller includes an input providing harvester engine and row unit operation signals, and wherein the controller is responsive to the operation signals to limit operation of the lift assembly when the row unit is not operating.

A harvester having a frame adapted for forward movement over a field and including a row unit supported for vertical movement relative to the frame by a hydraulic height control cylinder, height control structure for controlling the row unit comprising:

• a first proportional valve connected to height control cylinder and to a source of hydraulic fluid under pressure;
• a second proportional valve connected to the height control cylinder and to the source;
• a controller connected to the first and second proportional valves;
• a raise/lower switch and an adjustable row unit height selector connected to the controller;
• a height sensing transducer connected to the controller and providing a row unit height indication;
• wherein the controller is operable in an automatic height control mode and is responsive to the unit height indication and the height selector adjustment to provide an electrical control signal to the proportional valves to automatically maintain the row unit at a preselected operating height;
• and
• an electrohydraulic valve connected to the proportional valves, wherein the controller includes an input receiving a row unit operational status signal, the controller responsive to the signal for moving the electrohydraulic valve to a position preventing operation in the automatic height control mode when the signal indicates a preselected unit operational condition.