air source is placed and pressed in order to achieve pneumatic yarn threading application_number US 91901292 A description in the figures equal parts or parts of equal or equivalent function carry the same reference numerals although the method described hereinafter refers to frusto conical bobbins it is adaptable to bobbins of cylindrical or any other shape for the purpose of overall clarity those parts not necessary for understanding the invention are omitted from the figures in that they are already known and because they are not concerned in the operation of the present invention in the accompanying drawings 1 is the initial yarn portion unwound from the underlying bobbin 4 which has already been positioned on the lower hollow mandrel 40 in the spindle basket 7 the end of said initial yarn portion 1 is brought to the outside of the circular casing 6 of the twisting spindle 10 in order to place it in a transverse position in the slot 47 of the compressed air jet injector 9 this latter being rigidly fixed to the front frame 15 of the aligned spindles 10 of which one follows another 3 is the initial yarn portion unwound from the feed bobbin 2 5 is the upper end of the hollow mandrel 40 i e the lower unwinding head through the central bore 29 of which the yarns unwound from the feed bobbins 4 and 2 enter and slide to form the twisted yarn 8 is a yarn accumulator disc of known type on the spindle 10 12 is the duct through which the yarns.