OIL HYDRAULIC CRANE HAVING SCREW TYPE OIL HYDRAULIC ROTATING DEVICE

PURPOSE: An oil hydraulic crane having a screw type oil hydraulic rotating device is provided to obtain the sufficient rotary angle of a column part with reducing the volume of a rotating element and to improve the durability of the parts by preventing self-bending. CONSTITUTION: An oil hydraulic crane formed with a crane base loaded in a vehicle, a column part installed in the vertical upper part of the crane base and rotatably installed by a rotating element, a boom assembly connected with the upper end part of the column part for being elastically operated, and a hook installed in the boom assembly for pulling up heavy articles, wherein the oil hydraulic crane includes a housing(610) having the rotating element installed in the upper part of the crane base and an oil entrance hole(612) for enabling oil to come in and out, a rotary shaft(620) received in the inside of the housing and interlocked with the lower end part of the column part, a piston(630) engaged with the outer peripheral surface of the rotary shaft and vertically slid by the oil pressure supplied into the inside of the housing, and a guide axial rod(640) coupled with both parts of the piston for guiding the vertical sliding of the piston.