Abstract: Disclosed is a series and a series group of orthogonal gear reducers with motors. A motor cover is disposed separately from a gear box. In each of sub-series (frame number) wherein the gear boxes have the same fitting dimensions (sizes) to be mounted to a mating machines, the following requirements are satisfied: 1 The fitting dimension between the motor cover and the gear box is made constant; 2 An axial shifted amount between a hypoid pinion and a hypoid gear is made constant; 3 an outside diameter of the hypoid gear is made almost constant; and 4 a distance between the center of the hypoid gear, and the mounting surface for the motor cover and the gear box is made constant.

Abstract: An output shaft is a hollow shaft and passes through a gearbox. Holes for mounting also pass through the gearbox. The holes are located at the vertexes of a square or rectangle. And the output shaft, which is displaced (offset) relative to the square's (or rectangle's) center, is located on one diagonal of the square. This structure provides a variety of possibilities of assembling the gear device with a big motor, and the amount of projection of the faces of the gearbox from the output shaft can be kept as small as possible.

Abstract: A planetary reduction gear has an inscribe type planetary gear mechanism (100; 600) and a planetary gear mechanism (130; 630) combined therewith. The inscribed type planetary gear mechanism has an internally-toothed gear (108; 602) and a flange (115; 608) either one of which serves as an output member while the other serves as a stationary member. Rotation of the input shaft (131; 631) of the planetary gear mechanism is transmitted to a planet carrier through an externally-toothed sun gear (132; 635) and planet gears (133; 636) so as to rotate the planet carrier in the same direction as the direction of rotation of the input shaft. The rotation of the planet carrier is transmitted to the output member through at least one eccentric member (102a, 102b; 61a, 613b) and at leat one externally-toothed gear (103a, 103b; 601b) in the inscribe type planetary gear mechanism so that the output member is rotated in the direction counter to the direction of rotation of the planet carrier.