Abstract: A driving unit (1), comprising: a motor (10), a driven shaft (2) driven by the motor, and a transmission device (20) coupled between the motor and the output shaft and having one input shaft (21) and two rotational output members (22) and (23), wherein the ratio of transmission from the input shaft (21) to the first rotational output member (22) differs from the ratio of transmission from the input shaft (21) to the second rotational output member (23). The first rotational output member (22) is coupled to the motor housing (11) via a slip coupling (30). A helical spring (60) arranged so as to be coaxial to the motor presses the first rotational output member (23) against the motor housing (11), wherein that helical spring (60) engages the motor housing (11) via a pressure ring (50). This pressure ring (50) has a helical channel (52) for receiving the helical spring (60). The pressure ring (50) is rotatable to enable setting the maximum value of the moment that can be supplied to the output shaft (2).