Patent ID: 8460153

Claim:
A power tool comprising: a housing; a motor coupled to the housing, the motor having an output shaft; an output member; a power transmitting mechanism drivingly coupling the output shaft to the output member, the mechanism comprising a transmission having dual planetary stage with a sun gear, a first planet gear, a second planet gear, a planet carrier, a first ring gear and a second ring gear, the first and second planet gears being rotatably mounted on the planet carrier, the first planet gear being disposed between the motor and the second planet gear and having a pitch diameter that is smaller that a pitch diameter of the second planet gear, the first ring gear being meshingly engaged with the first planet gear, and the second ring gear being meshingly engaged with the second planet gear; and a shift mechanism having a collar that is non-rotatably but axially slidably coupled to the housing for movement between a first position and a second position, wherein the collar comprises an annular collar body, a first set of external splines and a second set of external splines, the collar body being received about the first ring gear, the first set of external splines extending radially inwardly from the collar body and engaging a third set of external splines formed about the first ring gear when the collar is in the first position to thereby inhibit rotation of the first ring gear relative to the housing, the second set of external splines being coupled to an end of the collar body that faces opposite the motor, the second set of external splines engaging a fourth set of external splines formed on the second ring gear when the collar is in the second position to thereby inhibit rotation of the second ring gear relative to the housing.