DEVICE FOR CONTROLLING WINCH OF EXCAVATOR

PROBLEM TO BE SOLVED: To provide a device for controlling a winch to reduce works by an operator and improve safety of operations by automatically switching between a constant velocity control and a control for preventing loosening of a rope causing irregular-winding of the rope in a winch system to lift excavation devices of construction machines by a constant velocity. SOLUTION: A differential pressure of hydraulic pressures at hoisting/ lowering sides of a hydraulic motor 6 is detected by pressure sensors 40, 42 and a motor load pressure is detected. When an excavating excavation device 11 reaches a bedrock and lowers its lowering speed, a pilot pressure 46 of a solenoid proportional pressure reducing valve 45 is regulated on the basis of decreases of the motor load pressure. When the motor load pressure further reduces even if a variable displacement pump 15 is at a minimum discharge rate, the winch 2 is stopped by a directional control valve 16. And when the motor load pressure re-increases by advancing of device 11, the winch 2 is re-rotated for controlling preventing loosening of the wire rope 3.