Of the coaxially arranged shafts 1 and 2 (see Figure), the torque is transmitted to the pivot axis mounted on balls. The adjustment of the ball axes 7 via a variable pulley 8 which is rotated in the circumferential direction over a Verstellschnecke 9th This is the position of the ball axes, which are guided on one side curved slots in the adjusting and are supported on the other side in radial grooves in the housing, changed evenly.