Electrohydraulic control of implement lift cylinders

Abstract

An implement lift system including a plurality of individual electrohydraulically controlled cylinders spaced on a tool frame and connected to lift wheel. An implement control unit (ICU) in the towing vehicle cab is connected to feedback potentiometers or similar transducers which provide signals corresponding to cylinder stroke length or suspension position. The feedback signals are compared at the ICU to a control signal obtained by rotation of a lever or knob on an operator control unit in the cab. Depending on the cylinder position relative to the operator selected position, the ICU provides an output signal to the electrohydraulic valve to achieve a proportional amount of flow for the desired cylinder position. The ICU also compares feedback signals from the transducers and adjusts the output voltage to each of the valves so that the frame can be raised and lowered evenly. In conditions where independent adjustment of different frame portions is desired, the operator control unit can be adjusted to provide the necessary offset signal for each section. The lift system provides uniform depth control and level lift for different frame configurations including frames with wings. Systems with dissimilar cylinders having different capacities or stroke lengths are easily accommodated.