and emptied again the compensating pulley 26 running downards for filling and upwards again for emptying this style of reservoir filling and emptying has the advantage that no separate expense has to be incurred for the drive systems for the spools 2 13 as regards their speed in adaptation to the speed of thread withdrawal if in fact it were intended to keep the reservoir constantly in a middle position it would have to be ensured by means of a special expensive regulating system that the drive systems of the spools 2 13 constantly run exactly at the speed corresponding to the speed of withdrawal by the knitting or weaving machine since thread spools are always wound with varying diameters so that the velocity of thread withdrawal fluctuates from spool to spool for a single spool rotational speed an individual regulated drive system would have to be provided for each spool in the present device fluctuation in the velocity of thread withdrawal during the running of the compensating pulley 26 from one extreme position to its other position are readily compensated for by the pulley 26 running upward or downward faster or slower in addition the tension of all threads 22 is kept constant in the present apparatus since the tension is dependent substantially solely upon the weight of the individual compensating pulleys 26 since these pulleys possess equal weights the tension of all the threads remain constant in fig2 there is illustrated a compensating pulley formed as double pulley consisting of the single.