| 摘要 |
An electric hoist includes an electric motor, a driving shaft connected to a rotor shaft of said electric motor, a reduction gear train for transmitting rotation of the driving shaft to a load sheave, and a mechanical brake assembly in the reduction gear train. According to the invention between the driving shaft and the rotor shaft of the motor is arranged an overload safety device comprising a support member fixed to the rotor shaft, a retainer member fitted onto the driving shaft, and a disc arranged between the support and retainer members through friction plates and having a one-way clutch. The one friction plate between the retainer plate and the disc has larger friction transmission force than that of the other friction plate between the support member and the disc. With this arrangement, the electric hoist according to the invention is able to automatically prevent lifting, lowering and dragging a load under overload condition, and enables the once raised load to be securely lowered irrespective of its light or heavy weight.
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