PURPOSE: To effectively supply lubricating oil to sliding surfaces by coupling a rotational transmitting mechanism to transmit the rotational force of a driving motor to a turntable with an oil-hydraulic pump by means of an electromagnetic clutch at the stoppage of electricity.

CONSTITUTION: A driving motor 1 to rotate a turntable 2 and a driving motor 19 to drive an oil-hydraulic pump 20 can not be operated at the stoppage of electricity, and a shaft 5 is coupled with a pump shaft 24a through a electromag netic clutch 26. In this case, the inertial rotation of the turntable 2 is transmitted to a pump 24 through gears 13, 15b, 11b 10, 7, and lubricating oil is supplied to the sliding surface of the turntable 2 through a part of pipe lines 22, 17 and a channel 16. In this course of time, force requied for driving the pump 24 acts as a load against the rotational force of the turntable 2, and rapidly weakens the rotational force, and finally the turntable 2 stops. Thus the lubricat ing oil can be effectively supplied to the sliding surface of the turntable.