Patent ID: 7143842

Claim:
A reciprocating power tool comprising: a tool bit that performs a predetermined operation on a workpiece by reciprocating, a driving motor that drives the tool bit and a power transmitting mechanism that converts a rotating output of the driving motor into linear motion in the axial direction of the tool bit, the power transmitting mechanism comprising: an internal gear rotatably supported to receive the rotating output of the driving motor all the time, a planetary gear driven by the rotating output of the driving motor to revolve around the center of the internal gear, a power transmitting part eccentrically disposed on the planetary gear, a rotation preventing mechanism that normally prevents rotation of the internal gear, the rotation preventing mechanism being adapted to allow rotation of the internal gear in relation to a load applied to the tool bit and to allow the internal gear to rotate by a predetermined degree and in a predetermined direction, whereby the relative position of the power transmitting part is changed with respect to a point of proximity of the planetary gear to the internal gear, so that a linear stroke of the power transmitting part in the axial direction of the tool bit is changed and an internal gear rotation lock that prevents the internal gear from rotating in a direction opposite to said predetermined direction.