A one-piece planetary carrier includes first and second side walls connected to one another by a plurality of webs. At least one of the webs has a curved outer surface which is directed substantially outward in a radial direction and belongs to a lateral surface of the web. The web includes a transition to the first side wall and a transition to the second side wall. The curved outer surface is convexly curved about a first axis of curvature at the transition to the first side wall and the transition to the second side wall. The curved outer surface has at least one anticlastic region which lies in an axial central section and an axial edge section of the web, with a combination of the axial central section with the axial edge section substantially defining an axial dimension of the planetary carrier.

A planetary transmission (2) includes a stepped planetary gear (24), or planetary gears, which are connected to each other, that is/are disposed radially between a first shaft (6) and axially-adjacent first and second ring gears (12, 16). The stepped planetary gear, or connected planetary gears, include(s) a first gearing region (26) that meshes with a sun gear (8) on the first shaft (6) and the first ring gear (12), as well as a helically-toothed second gearing region (28) that meshes with the second ring gear (16). A cylindrical support region (32) is coaxially provided on/around the first shaft. The stepped planetary gear or the connected planetary gears is/are supported on the cylindrical support region of the first shaft by the outer circumferential surface of the second gearing region. The second gearing region lies on the addendum circle of the second gearing region.

A planetary transmission (2) includes a stepped planetary gear (24), or planetary gears, which are connected to each other, that is/are disposed radially between a first shaft (6) and axially-adjacent first and second ring gears (12, 16). The stepped planetary gear, or connected planetary gears, include(s) a first gearing region (26) that meshes with a sun gear (8) on the first shaft (6) and the first ring gear (12), as well as a helically-toothed second gearing region (28) that meshes with the second ring gear (16). A cylindrical support region (32) is coaxially provided on/around the first shaft. The stepped planetary gear or the connected planetary gears is/are supported on the cylindrical support region of the first shaft by the outer circumferential surface of the second gearing region. The second gearing region lies on the addendum circle of the second gearing region.

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.

Provided is a friction transmission device including an input raceway ring, a planetary rolling element that is disposed around a rotation axis of the input raceway ring and comes into contact with the input raceway ring; an output raceway ring that comes into contact with the planetary rolling element and is connected to an output shaft, and a first support raceway ring and a second support raceway ring that come into contact with the planetary rolling element. A quadrangle is formed by extension lines of normal vectors at contact points between the planetary rolling element and the respective raceway rings.

Provided is a friction transmission device including an input raceway ring, a planetary rolling element that is disposed around a rotation axis of the input raceway ring and comes into contact with the input raceway ring; an output raceway ring that comes into contact with the planetary rolling element and is connected to an output shaft, and a first support raceway ring and a second support raceway ring that come into contact with the planetary rolling element. A quadrangle is formed by extension lines of normal vectors at contact points between the planetary rolling element and the respective raceway rings.

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 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.