Reducer with Oldham coupling

A reducer in combination with a nonreturn device and with an Oldham coupling comprising at least one planetary reduction stage seated in a cylindrical casing, wherein a movable output member of a last reduction stage consists of a first tubular seat with a cylindrical wall, said cylindrical wall has an interruption, a second tubular seat seated in said first tubular seat, said second tubular seat having externally a radially projecting part engaged in the interruption of the first tubular seat for driving said first tubular seat in rotation, said second tubular seat having an internal diametral groove in which one of the sides of an Oldham cross is engaged, said Oldham cross being seated entirely within the, second tubular seat, the nonreturn device consists of a helical spring which surrounds the first tubular seat and has ends attached to each of the edges of said interruption, the first and second tubular seats being located within the cylindrical casing of the reducer, and the first and second tubular seats and an output member of the Oldham coupling are retained axially in said casing by a retaining ring fastened to the end of said casing, and nonreturn braking being ensured by laying the spring against the casing.