Importance

Loading Importance Indicators...

Abstract

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 casing fitted through a one-way clutch onto the rotor shaft, a first support member fixed to the rotor shaft, a second support member slidably fitted on the driving shaft, a retainer member fixed to the casing, friction plates respectively arranged between the first and second support members and between the second support member and the retainer member, and dish-shaped springs for urging the retainer member against the first support member, thereby transmitting torque through one of the friction plates in raising a load and through both the friction plates in lowering the load and effecting such a changing-over by means of the one-way clutch. 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.

Loading the Abstract Image...

First Claim