Patent ID: 6891457

Claim:
A power tool comprising: a battery, a solenoid coil storing the electrical energy supplied from the battery as magnetic energy, a switch electrically connecting and disconnecting the battery with the solenoid coil, a plunger for striking a faster, the plunger being attracted by electromagnetic force stored in the solenoid coil and moving from a first position to a second position, wherein the plunger strikes the fastener when the plunger reaches the second position, means for retaining the plunger in the first position, and a controller coupled to the switch and the retaining means, the controller ( 1 ) turning on the switch when the plunger is retained by the retaining means in the first position, and ( 2 ) turning off the retaining means in order to stop retaining the plunger when the current flowing through the solenoid coil reaches a predetermined value.