The invention relates to a slewing mechanism and particularly relates to a slewing mechanism for the fields of
tower cranes. The invention provides the slewing mechanism which is simple in structure and low in cost, and is capable of realizing stepless speed adjustment, stably starting and braking and reducing impacts to a crane boom and a
tower body. The slewing mechanism comprises an alternative current (AC) motor, a slewing speed
reducer, an electromagnetic eddy
clutch, an electromagnetic eddy
brake, a middle electric pivot, an
electric control system and an operation platform. During starting, the middle electric pivot is smoothly started by virtue of the comprehensive actions of the electromagnetic eddy
clutch and the electromagnetic eddy
brake; the inertial
impact during starting is avoided; during braking of the slewing mechanism, the
brake time of the slewing mechanism is prolonged by virtue of the electromagnetic eddy
clutch and the electromagnetic eddy brake; the stable transition of the slewing mechanism from a motion state to a motion state is realized and the impacts to the crane boom and the
tower body during braking are reduced.