CONTROLLER FOR WINDING DRUM OF CRANE

PURPOSE:To prevent the complicated form in the control of an earth drilling machine or vibration type pile striking machine by installing a device for preventing the random winding on a winding drum which is generated by the slackening of a winding drum cable in the lowering and grounding of an excavating tool at the lower edge of a carry bar and the pile on a vibration type piling machine. CONSTITUTION:A pilot check valve 4 and a relief valve 5 are connected in series between a high pressure side oil passage and a low pressure side oil passage during hoisting between a winch motor 1 and a counterbalance valve 3. A selector valve 8 is connected in the high pressure side oil passage through a check valve 6. When the primary side of the check valve 6 is allowed to communicate to a tank T by the selector valve 8, the check valve 6, pilot check valve 4, or relief valve 5 are closed in the hoisting or lowering drive of the winch motor 1 by a direction selecting valve 2. Further, when the primary side of the check valve 6 is connected to a hydraulic source by the selector valve 8, at a neutral position of the direction selector valve 2, the check valve 6, pilot check valve 4, and the relief valve 5 are opened, and the hydraulic pressure in the oil passage formed between the motor 1 and the counterbalance valve 3 is kept at the random winding preventing pressure of a winding trunk cable.