Patent attributes
A machine tool includes a tool and a protective device. The tool includes a saw blade and a motor for driving the saw blade. An insulating member is arranged between the saw blade and the motor. The protective device includes a signal receiving unit, a control unit and a breaker. The signal receiving unit has an antenna receiving end that is in electrical contact with a middle region of the saw blade. The breaker is electrically connected between the motor and a utility power supply. The control unit is connected to the signal receiving unit and the breaker. The saw blade is used as an antenna by the signal receiving unit to receive an electromagnetic wave having the same frequency as that of a utility power from an environment, and the control unit controls the breaker according to a change of intensity in the electromagnetic wave.