In the power distribution work using the indirect live-line method, it is necessary to frequently lift a tool weighing 15[kg] and hang it on the electric wire. To reducing the load on workers, this paper proposed a motor-less power assist device that can compensate the weight of the tool in the wide range of motion: vertical 600[mm], horizontal 600[mm], pitch 90[deg]. The device has weight of 16[kg] and depth of 200[mm], which is lighter and more compact than conventional ones, so that it can be mounted on the side of the bucket of aerial work platform. To verify the effectiveness of this device, we measured the surface myoelectric potential of the forearm flexor muscle group during the overhead wiring work and the time required for the work. Through the experiments, it was confirmed that the load on the muscles was reduced by 90% or more by using this device, and the working time was almost same as the case without assistance.
