To spin-draw thermoplastic filament yarns such as polyesters, polyamides and the like, drawing devices having two or more pairs of rolls or godets (DE-A 1 907 782) are used. The axes of rotation of the rolls within the godet pair units are slightly inclined to each other to produce a certain winding pitch of the laid-on thread. Accordingly, the two axes of rotation lie within a common plane. Any change in the winding pitch required can easily be undertaken by changing the angle which the two axes of rotation together form.
It is also known that in a pair of godets, the axes of rotation of the two godets can be pivoted within two different planes, which are parallel to each other, perpendicular to the line connecting the godet axes.
It has been shown that neither the one nor the other of the described axial arrangements is optimal for the simultaneous spin-drawing of more than one thread.
It has been found that the winding pitch of the thread loops on one pair of rolls becomes smaller, the further the filament yarn is laid on towards the front, free end of the rolls. When only one filament yarn is being handled on a drawing frame, this is not of importance. When two or more filament yarns are handled simultaneously, a systematic reduction takes place in the spacings between the thread loops laid on parallel to each other the pair of godets. This reduction propagates itself to each downstream pair of godets, so that when three or more pairs of godets are used, the spacings between the filament yarns become so small that they can no longer be separated or no longer be sufficiently separated from each other. In the spin-drawing of multifilaments, it can moreover occur that individual fibrils from a filament yarn cross over to the neighboring filament yarn; as a result, differences in linear density are caused in the filament yarns which are produced simultaneously in this manner. Furthermore fibril breaks or thread breaks are caused by this on the drawing frame, which influences both the filament yarn quality and the economic efficiency of the process.
USPTO Backgrounds
USPTO Backgrounds