invention therefore makes it possible to limit the tensions in the weft 30 and thereby to reduce the number of weft ruptures the relative alignment of the thread brake 2 and the thread eyes 8 9 to the main airjet nozzle limits tension spikes at the beginning of weft insertion while tension spikes arising when abruptly starting the thread brake 2 are limited by a relative motion between the drive means and the thread guides 24 37 39 46 49 and the tension spike produced at the end of weft insertion namely when the weft 30 is locked in place by the pin 9 returning to the winding drum 7 is reduced because the thread brake 2 has by the time the pin is returned already partly decelerated the weft 30 furthermore those skilled in the art will appreciate that the desired tension in the wefts 30 may be adjusted by exchanging the transmissions 24 37 39 46 49 for others producing different tensions for example springs of one kind may be replaced with springs having different spring constants if a spring similar to the illustrated spiral spring 24 is used several turns may be joined to each other to thereby alter the spring constant moreover if the permanent magnet transmission of fig1 is used certain permanent magnets may be replaced with others of different field strengths and the number of permanent magnets may be varied as noted above in yet another variation more than two thread guides 20 21 may be provided for example four thread guides may be used which would be symmetrically mounted in pairs relative to the drive shaft 25 but at different distances from.