and its stroke drive 9 as well as the cable drums 21 for winding the bearing cables 14 and the auxiliary cables 15 and their stroke drive 8 are mounted on a common horizontal platform 19 fig4 the platform 19 is set in rotation about the axis of the pulling cable 6 by the rotation drive 10 the drives 8 and 9 are therefore capable of driving the vertical movement of the pulling cable 6 and the synchronous vertical movement of the cables 14 15 of the supporting device independently of one another since the relief of the thin neck portion 11 is intended to be initiated in a controlled manner after the gripping catches 18 have made contact with the bicone 13 of the single crystal 5 it is possible to insert above the cable drums 7 21 guide rollers 24 25 over which the cables 6 14 15 run and the bearings of which are each connected to load cells so that electronic signals relating to the loading due to the weight of the individual cables are available at any time in order to ensure that all the cables 6 14 15 each run perpendicular to the guide rollers 24 25 it is advantageous for the cable drums to be mounted on their drive shafts 22 23 such that they can be displaced laterally and if appropriate adjusted when the cables are wound on and unwound the movement of the cables 14 15 in relation to one another in order to pivot the gripping catches could be achieved by using in each case one separate.