Hydraulically powered hoist for harvesters and tractors - has closed loop control to maintain accuracy of implement motion

摘要

A hydraulic control circuit is used to provide control of the motor of an actuator used on a tractor or thresher. The linear actuator (22) operates over a linkage (21) to move the plough or other tool to a required position. Feedback is provided for both the plough (X2) and for the actuator (X1). A simulator (13) responds to both the feedback signals and the setting of a manual lever (11) indicating required position. An output rod operates on an adjusting actuator (27) that receives force feedback (36) on the load and operates to offset a control unit (31) to regulate flow. A valve (41) is switched to pass flow from a pump (45) to the load. In the reset position flow is passed back to the tank.