Power tool

A power tool comprising:

• a tool body;
• a tool holder;
• a tool bit coupled to the tool holder;
• an actuating mechanism disposed in the tool body to drive the tool bit linearly by means of pressure fluctuations so as to cause the tool bit to perform a predetermined operation, wherein the actuating mechanism has a driving motor, a motion converting mechanism that converts a rotating output of the driving motor to a linear motion, a piston linearly reciprocating in a longitudinal direction of the tool bit via the motion converting mechanism, a striker disposed in front of the piston to cause the tool bit a linear motion, a first chamber between the striker and the piston, and a second chamber disposed adjacent to the piston within the tool body in an opposite side of the first chamber;
• a dynamic vibration reducer having a weight that reciprocates under a biasing force of an elastic element to reduce vibration of the actuating mechanism, the weight being driven by means of pressure fluctuations caused in the second chamber when the piston reciprocates;
• and
• a cylinder that houses the striker such that the striker slidingly reciprocates within the cylinder,
• wherein the cylinder moves between a first position near the tool holder and a second position remote from the tool holder than the first position, and under loaded driving conditions in which a load associated with the predetermined operation is applied to the tool bit, the cylinder moves to the second position so as to allow the weight to be driven by means of fluctuating pressure within the second chamber, while, under unloaded driving conditions in which a load associated with the predetermined operation is not applied to the tool bit, the cylinder moves to the first position so as to prevent the weight from being driven by means of fluctuating pressure within the second chamber.