Patent ID: 7886509

Claim:
A power-driven grass mower comprising: an operation division comprising a moving grass cutter; and a motor division comprising an electric motor through which the operation division is driven, the electric motor comprising a Hall element; wherein the grass mower further comprises a control division through which it is determined if the motor division is locked by detecting speed at which the electric motor operates based upon detection of pulse signals generated by the Hall element, the Hall element generating either: a) a predetermined too few pulse signals; or b) no pulse signals in the event that the motor division becomes locked, in response to which the motor division is placed into an inching operation mode, the motor division in the inching operation mode causing the grass cutter on the operation division to move in cycles wherein the operation division repeatedly starts and stops, the grass cutter being moved for 0.1 to 0.5 sec and stopped for 0.5 to 0.9 sec in each cycle.