does not bear directly against the inner side of the collar 19 but rather is mounted in the collar 19 with the interposition of the securing ring 43 and as a result the driver 21 is mounted on the second fitting part 12 on the outer side of the fitting part having the plain bearing bushing 28 in the present case the first fitting part 11 a sealing ring 44 for example made of rubber or soft plastic is provided between the radially outer border of said fitting part and the covering disk 25 and is connected in particular clipped to the covering disk 25 the sealing ring 44 can also be formed from metal and fixedly connected for example welded to the first fitting part 11 wherein the covering disk 25 is then movable relative to the sealing ring 44 a separating ring 45 is optionally provided within the construction space between the two fitting parts 11 and 12 as an internal seal said separating ring being composed for example of plastic the wedge segments 27 and the spring 35 define an eccentric which as an extension of the direction of eccentricity presses the toothed wheel 16 into the toothed rim 17 at an engagement point during drive by means of the multiply rotating drive shaft 7 a torque is first of all transmitted to the driver 21 and by means of the driver segment 29 is then transmitted to the eccentric which is defined in this manner and which slides along the plain bearing bushing 28 displacing the direction of eccentricity and therefore displacing the engagement point of the toothed wheel 16 in the toothed rim 17 which is represented in the.