Patent EP-0635591-A1 (EP)
Inventor: BOENIGK BURKHARD DR
IPC: D02J1/08
Filed: 1994-07-18
Abstract: What is described is a multifilament smooth yarn which has a low tendency of the interconnected filaments to open out, expressed by the quantity  VS(KF)>42%,  and which has coherence, expressed by the quantity  (VGmean/VGmax)*100%>45%. The quantities VG represent degrees of swirling, determined by the Rothschild needle tester type 2040, VGmean represents the mean needle-test value as an arithmetic mean of 20 measured values, and VGmax represents the maximum needle-test value as the highest value of 20 measured values. The quantity VS(KF) represents the swirl stability for a predetermined total thread tension KF, which is determined by measuring the tendency of the multifilament smooth yarn to open out under dynamic mechanical stress according to the following method:   a) determination of the degree of swirling VGinit of the multifilament smooth yarn to be tested by the Rothschild needle tester R 2040, b) presentation of the multifilament smooth yarn in a test zone of specific length, in which the yarn path experiences a deflection, which test zone is formed at the start and end by transport devices for the yarn and by a radial-force measuring device arranged between the transport devices, the angle between the two parts of the yarn path being approximately 50 DEG  to approximately 5 DEG , and the deflection being caused by the arrangement of the transport devices and of the radial-force measuring device and the movement of the multifilament smooth yarn through the test zone taking place under a predetermined static thread pull, c) periodic deflection, at a frequency corresponding to the shed-changing frequency of a weaving machine, especially 8 to 35 Hertz, of the multifilament smooth yarn moving through the test zone, the said periodic deflection taking place perpendicularly to the yarn axis over a predetermined length by means of a deflection device which acts within the test zone on the multifilament smooth yarn to be tested, in such a way that, during maximum deflection, there results in the multifilament smooth yarn a total thread tension KF of 0.1 to 1.0 cN dtex which is composed of a fraction of the static thread pull and a fraction of the dynamic thread pull periodically acting on the yarn and caused by the deflection, d) determination of the thread pull KF acting on the multifilament smooth yarn during its run through the test zone, by means of the radial-force measuring device, there being assumed as KF the force which acts on the multifilament smooth yarn between two deflections of the latter by means of the deflection device, e) determination of the degree of swirling VGfinal of the yarn treated in the test zone by means of the Rothschild needle tester R 2040, and f) determination of the swirl stability VS for a predetermined total thread tension KF according to the relation  VS(KF)=(VGinit/VGfinal)*100(%).   Furthermore, a method for production of size-free weavable and swirled multifilament smooth yarns is described. The method comprises the measures   i) presentation of at least one single-component or multi-component multifilament roving and the feed of this multifilament roving to at least one swirling nozzle, ii) swirling of the multifilament roving in the swirling nozzle by means of fluid, preferably air, with such a lead of the multifilament roving and under such a pressure of the swirling fluid that an essentially smooth swirled multifilament yarn forms, and iii) drawing-off of the swirled multifilament smooth yarn out of the swirling nozzle, with the proviso that the tension of the yarn is selected so that, at the swirling point, the latter is under a tension of smaller than or equal to 0.6 cN/dtex