Patent ID: 7996996

Claim:
A reciprocating power tool, comprising: a motor, a tool bit that performs a predetermined operation by reciprocating, a slider that reciprocates to drive the tool bit, a motion converting mechanism that converts a rotating output of the motor into a reciprocating movement of the slider, the motion converting mechanism comprising a rotating crank disc comprising a slider driving part and further comprising a counterweight driving part and a crank pin disposed on opposite sides of the center of rotation of the crank disc, wherein the crank disc has a circular contour, a stepped portion and a thick wall portion, wherein the stepped portion is formed in the circumferential or radial direction of the crank disc and the thick wall portion is formed around a hole that penetratingly extends through the crank disc, the thick wall portion having a larger thickness in the thickness direction of the disc than the other parts of the crank disc a counter weight separate and distinct from the crank disc that reciprocates in a linear direction opposite to the reciprocating direction of the slider to reduce vibration caused by the reciprocating movement of the slider in a first vibration reducing function, a vibration alleviating mechanism defined by a portion of the crank disc having a component of motion in a direction parallel to the reciprocating movement of the slider to perform a second vibration reducing function together with the first vibration reducing function to reduce vibration, wherein a line connecting the center of rotation of the crank disc and a center of the crank pin is inclined by an angle in the direction of rotation of the crank disc with respect to a line connecting the center of rotation of the crank disc and a center of the counterweight driving part, and wherein the crank disc is coupled to the slider by means of the crank pin and the center of gravity of the crank disc fitted with the crank pin without the counterweight is located at a position offset from the center of rotation of the crank disc toward the counter weight when the counter weight is in a position remote from the tool bit to provide the second vibration reducing function.