Patent ID: 8469115

Claim:
An electrical power tool comprising an electric motor operated by a triggering operation of the switch lever; and a speed change device for decelerating rotative power of the electric motor and outputting the same to a spindle, wherein the speed change device has a first stage planetary gear train positioned in an upstream side of a power transmission pathway, a second stage planetary gear train positioned in a downstream side of the power transmission pathway, and an internal restriction member capable of preventing an internal gear of the second stage planetary gear train from being rotated about an axis, wherein the speed change device is constructed such that when an external torque applied to the spindle is increased, an initial condition in which the internal gear is allowed to rotate so that a high speed low torque is output to the spindle can be automatically switched to a condition in which the internal gear is prevented from rotating by the internal restriction member so that a low speed high torque is output to the spindle, wherein the speed change device includes a mode lock mechanism that is capable of maintaining the automatically switched low speed high torque output condition regardless of changes of the external torque, and a reset mechanism that is capable of releasing the mode lock mechanism such that operation modes can be returned to the initial condition, and wherein the reset mechanism is actuated by an actuator that is provided separately from the switch lever as a drive source.