Patent ID: 8016047

Claim:
An electrical power tool comprising: a motor having a drive shaft; a casing accommodating at least the motor; a piston driven by a rotary motion of the drive shaft; an intermediate shaft extending parallel to the drive shaft and driven to rotate by the rotary motion of the drive shaft, the intermediate shaft defining an axial direction; a motion conversion mechanism disposed on the intermediate shaft and capable of moving in association with the intermediate shaft for converting the rotary motion of the drive shaft to a reciprocating motion, the motion conversion mechanism comprising a first motion conversion mechanism that is connected to the piston and moves the piston in a reciprocating motion in directions substantially parallel to the axial direction of the intermediate shaft; and a plurality of anti-vibration mechanisms of different types accommodated in the casing; wherein the plurality of anti-vibration mechanisms of different types comprise at least one compulsive anti-vibration mechanism and at least one passive anti-vibration mechanism; wherein the compulsive anti-vibration mechanism includes a first counterweight capable of reciprocating in directions substantially parallel to the axial direction of the intermediate shaft in opposite phase to and in interlocking relation to the reciprocating motion of the piston; wherein the passive anti-vibration mechanism includes a second counterweight capable of reciprocating in directions of the reciprocating motion of the piston due to a vibration applied to the motor and the casing; wherein the motion conversion mechanism further comprises a second motion conversion mechanism; and wherein the first counterweight is connected to the second motion conversion mechanism so as to be capable of reciprocating in opposite phase to the reciprocating motion of the piston.