Patent ID: 7204322

Claim:
A power tool comprising: a variable speed rotational driving motor controlled by a controller, a driver driven by the variable speed rotational driving motor to cyclically reciprocate, a cylinder having a wall defining a cylinder bore disposed within the power tool, the driver cyclically reciprocating within the cylinder bore, and a tool bit linearly driven by utilizing the pressure of air within the cylinder bore of the power tool, the pressure being created by the cyclical reciprocating movement of the driver within the cylinder bore, wherein the controller changes the rotational speed of the variable speed driving motor, thereby changing the cyclical reciprocation speed of the driver within the cylinder bore, thereby alleviating vibration caused by pressure fluctuation of an air compressed by the driver within the cylinder bore, wherein the rotational speed of the variable speed driving motor is increased by a predetermined amount according to the position of the driver when the driver is driven in a direction away from the tool bit, and wherein the increase of said rotational speed is compensated for by decreasing the rotational speed of the variable speed driving motor by a predetermined amount when the driver is driven in a direction toward the tool bit.