Abstract: A sealed rotary transmission device comprises a control shaft and a receiver shaft parallel to and spaced from the control shaft. A bellows surrounds the receiver shaft, and has one end fixed in a sealed way to a casing of the device. The device also includes a transfer member constrained to move parallel to a plane perpendicular to the receiver shaft. The other end of the bellows is fixed to this transfer member in a sealed way. On each of the control and receiver shafts is a respective crank, eccentric to its axis by the same distance. These cranks are coupled to the transfer member and spaced by the same distance as the shafts. This enables circular translation of the transfer member.