L48A1 Mast SectionThe reason of the broken shaft of the rotary motor caused by the reverse rotation of the tower crane during the rotary positioning
If the construction site in the tower crane rotation positioning, the use of rapid reverse measures, that is, commonly known as "reverse car", which makes the whole rotation mechanism in the bearing of normal rotation torque, and suddenly increased a reverse starting torque, which greatly exceeds the rotation mechanism can bear the rated torque. Although the input shaft of the rotary reducer is smaller than the output shaft of the rotary motor, the output shaft of the rotary motor will be broken due to excessive torque because the hydrostatic dump type hydraulic coupling can isolate vibration and mitigate impact.
At present, the slewing machinery of tower crane in China generally adopts the structure of motor hydraulic coupling slewing reducer slewing bearing. The large-scale tower crane up rotation motor adopts frequency conversion speed regulation or winding rotor asynchronous motor to reduce the rotation start speed and the rotation start torque of the tower crane. Due to the limitation of production cost, the small and medium-sized tower crane mostly adopts asynchronous motor or multi speed asynchronous motor and only relies on the hydraulic coupling to mitigate the start impact, but the hydraulic coupling used is generally static pressure dump type As a result, the rotating starting torque of small and medium-sized tower crane is large, and the whole mechanism can not be effectively protected against dynamic overload.
