Speed reduction unit

A speed reduction unit comprising an outer casing, an input shaft and an output shaft coaxial with respect to one another and rotatably supported by said casing, a first gear integral with said output shaft, a second gear coupled with said first gear, and connection means between said second gear and said input shaft, the number of teeth of said two gears differing from one another by at least one tooth;

• and in which said first gear is a face gear and said second gear is a bevel gear sloping with respect to the first gear and positioned to face it, said second gear being centrally supported inside said casing by means of a ball joint support in order to oscillate relative to said casing and said first gear about a point of the common axis of said two shafts, said connection means comprising a central axial projection extending from said second gear, key means being provided for angularly locking said second gear relative to said casing, said ball joint support comprising an upright extending axially from said first gear towards said second gear and a ball interposed between the free end of said upright and said second gear, a first seating spherical in shape for said ball being formed on said upright, a second seating spherical in shape for said ball being formed centrally on said second gear.