Patent ID: 8713806

Claim:
A power tool comprising a power source, a speed change mechanism and a tool bit which is driven by the power source via the speed change mechanism so as to perform a predetermined operation, wherein: the speed change mechanism comprises first and second rotating shafts and first and second gear trains, the first and second rotating shafts being disposed parallel to each other, the first and second gear trains having different gear ratios and each having a combination of a drive gear and a driven gear as one unit which are engaged with each other and transmit torque of the first rotating shaft to the second rotating shaft, wherein a torque transmission path via the first gear train is defined as a first power transmission path and a torque transmission path via the second gear train is defined as a second power transmission path, wherein the speed change mechanism further includes a first clutch which allows and interrupts power transmission on the first power transmission path and a second clutch which allows and interrupts power transmission on the second power transmission path, the power transmission path is switched between the first and second power transmission paths while the first and second gear trains are held engaged, by shifting of the first and second clutches between the power transmission state and the power transmission interrupted state according to a load applied to the tool bit, and the speed change mechanism includes a switching retaining mechanism, and when the power transmission path is switched between the first and second power transmission paths, the switching retaining mechanism retains the shifted state until the power source is stopped.