A power tool includes a motor and a gear speed reducer. The motor has a motor shaft that is rotatable in a normal direction and in a reverse direction. The gear speed reducer is operably coupled to the motor shaft. The gear speed reducer is configured such that a reduction ratio of the gear speed reducer is changed in response to a change of a rotation direction of the motor shaft.

Provided is a wind power generation transmission system. A first sun gear is a hollow gear. The first sun gear includes a first end surface and a second end surface opposite to the first end surface. A second planetary carrier includes a third connection end. An outer circumferential surface of the third connection end is provided with external splines. An inner circumferential surface of the first sun gear is provided with internal splines. The third connection end of the second planetary carrier extends from the second end surface to the first end surface and is disposed in the first sun gear so that the external splines of the third connection end are connected to the internal splines of the first sun gear.

Provided is a wind power generation transmission system. A first sun gear is a hollow gear. The first sun gear includes a first end surface and a second end surface opposite to the first end surface. A second planetary carrier includes a third connection end. An outer circumferential surface of the third connection end is provided with external splines. An inner circumferential surface of the first sun gear is provided with internal splines. The third connection end of the second planetary carrier extends from the second end surface to the first end surface and is disposed in the first sun gear so that the external splines of the third connection end are connected to the internal splines of the first sun gear.

A torque transfer device has plural planets arranged for planetary rotation about one or more sun gears and within one or more ring gears. Each planet includes at least one planetary gear set comprising plural planetary gears connected to rotate together, but having a different diameter to form a differential gear system. To improve load sharing, the plural planetary gears of each planetary gear set may have a different helical angle, the plural planetary gear sets being axially movable with respect to one another. Alternatively or in addition, the planetary gears may be made flexible with respect to radial forces.

A tool with two sequential gear trains and gear carrier assemblies adapted to be recessed into internal gears. The internal gear assembly also prevents rotation of the internal gear assembly relative to a housing of the tool. For example, the internal gear assembly can include a first gear train and second gear train sequentially coupled to the first gear train, wherein a first ring gear and first planet gears of the first gear train are substantially similar to a second ring gear and second planet gears of the second gear train.

A tool with two sequential gear trains and gear carrier assemblies adapted to be recessed into internal gears. The internal gear assembly also prevents rotation of the internal gear assembly relative to a housing of the tool. For example, the internal gear assembly can include a first gear train and second gear train sequentially coupled to the first gear train, wherein a first ring gear and first planet gears of the first gear train are substantially similar to a second ring gear and second planet gears of the second gear train.

The invention relates to a wind turbine comprising a hub, a nacelle, a tower and a power transmission system for increasing the rotational speed from said hub, said power transmission system comprising at least a first and a second epicyclic gear stage, each of said epicyclic gear stages including a ring gear, a planet carrier and a plurality of planet gears, said plurality of planet gears being mounted in the planet carrier and engaging with the ring gear and with a sun gear; wherein each of said plurality of planet gears of at least said first epicyclic gear stage and said second epicyclic gear stage have identical gear profile design parameters.

An energy harnessing device for harnessing wave energy that results in pitch, sway, yaw, surge, roll, and heave movement, wherein the device effectively converts multiaxial translational and rotational motion to unidirectional rotational motion for power transmission.

An energy harnessing device for harnessing wave energy that results in pitch, sway, yaw, surge, roll, and heave movement, wherein the device effectively converts multiaxial translational and rotational motion to unidirectional rotational motion for power transmission.

Methods and systems for an electric axle assembly are provided herein. The electric axle assembly includes, in one example, an electric machine with a rotor shaft having an output gear thereon. The electric axle assembly further includes a planetary gearset with a carrier coupled to a pair of axle shafts, a first ring gear with external teeth that are rotationally coupled to the output gear; and a sun gear meshing with a plurality of planet gears that rotate on the carrier, where, in the axle assembly, internal teeth of the ring gear are rotationally coupled to the plurality of planet gears, and where, in the axle assembly, the sun gear or the carrier are grounded by a housing of the electric axle assembly.