| 摘要 |
In an electrical tool having a clutch for adjusting rotational torque of the driven shaft, a limit switch of double-throw type is used for detecting the state of the clutch, and a capacitor is arranged to be charged via the limit switch. In one embodiment of the instant invention, the capacitor is normally discharged and is charged when the clutch assumes a disengaged state, thereby producing a trigger pulse used for making a short circuit for the motor only when the capacitor is not fully charged. In another embodiment, the capacitor is normally charged, and is discharged when the clutch assumes a disengaged state, thereby producing a trigger pulse used for making a short circuit for the motor. With this arrangement a switching circuit provided for making the short circuit for the motor is effectively prevented from making the short circuit when a power switch is turned on irrespective of the state of the clutch. |
