Casing rotator

A casing rotator comprising:

• a base frame configured to be installed on a ground;
• a lifting frame provided above the base frame to be liftable and lowerable via four lifting cylinders;
• a chuck mechanism configured to be lifted and lowered along with the lifting frame;
• a rotation transmission mechanism configured to apply a rotating force to a casing held by the chuck mechanism;
• and
• control means configured to perform control of leveling the lifting frame, wherein
• the four lifting cylinders are hydraulic cylinders that are arranged at four corners of a virtual quadrilateral defined along an outer edge of the lifting frame in a plan view and that are capable of performing a contracting action of applying a press-in force to the casing and an extending action of applying a pull-out force to the casing, and
• the control means includes
• a tilt sensor configured to detect a change angle of tilt of the lifting frame with respect to a leveled state,
• four variable throttle valves forming pairs with the four lifting cylinders, respectively, and provided in flow passages through which a hydraulic oil flows out from the respective lifting cylinders in a contracting action state of the lifting cylinders, and
• a control unit configured to individually adjust throttling degrees of the respective variable throttle valves based on the change angle detected by the tilt sensor.