US Patent 7469753 Power tool, drive assembly, and method of operating the same

A power tool including a drive assembly including a first clutch assembly having an engaged configuration, in which the first clutch assembly transfers a drive force from a motor shaft to a spindle, and a disengaged configuration, in which the first clutch assembly prevents the transfer of the drive force. The first clutch assembly can be movable toward the disengaged configuration when a torque exerted on the spindle exceeds a torque limit. The drive assembly can also include a second clutch assembly having an engaged configuration, in which the second clutch assembly transmits the drive force from the motor shaft to the spindle, and a disengaged configuration, in which the second clutch assembly prevents the transmission of the drive force. The second clutch assembly can be movable toward the engaged configuration when the tool element engages a workpiece.