Patent GB-784535-A (GB)
Title: Improvements in and relating to the cold stretching of synthetic filaments
IPC: D02J1/22
Filed: 1955-02-16
Abstract: Artificial filaments, e.g. of polyamides or polyesters, are cold-drawn in a dry condition by axially advancing the unstretched filaments at a predetermined feed speed in the feeding zone of a filament-advancing and storage device along a first helical path comprising a plurality of loops parallel with one another, a portion of each loop being in contact with a positively driven cylindrical roller of circular cross-section over an are subtending an angle greater than 180 degrees, and another portion of each loop sliding over and making frictional contact with a fixed surface, and successively advancing the filaments at a stretch speed which is a multiple of the feed speed corresponding with the stretch <PICT:0784535/IV (a)/1> <PICT:0784535/IV (a)/2> ratio, in a stretching zone of the filament-advancing and storage device, along a second helical path comprising a plurality of loops parallel with one another, a portion of each loop being in contact with a second cylindrical roller of circular cross-section over an arc subtending an angle greater than 180 degrees, and another portion of each loop sliding over and making frictional contact with a second fixed surface, the second roller being coaxial and contiguous with the first roller and the second helical path immediately following the first so that there is practically no free path to be covered by the filments in passing from the feeding zone to the stretching zone of the filament-advancing and storage device.  As shown in Fig. 1, an unstretched 60 denier monofil of polycaprolactam 12 travels at a feed speed of 300 metres per minute from the bobbin 11 to form a helix of loops 13a passing round the driven feed roller 14 and a fixed rod 15 whose axes are mutually inclined.  From the point 16 on the feed roller 14 the filament 13c, after passing round the rod 15, passes to the draught roller 18 which is driven at a peripheral speed of 1200 metres/minute and over the fixed rod 19, which is inclined with respect to the roller 18, to form a series of loops 17a and 21, the denier of the filament on leaving the rod 19 being reduced to 15. The rollers 14 and 18 are coaxial and contiguous, roller 18 having a somewhat smaller diameter than roller 14 and being rotatable independently of roller 14.  The diameter of the draught roller may, however, be equal to that of the feed roller or may be greater, as shown in Fig. 3, in which the filament 22 passes from the bobbin 30 first round the feed roller 24 and the right-hand portion of the inclined fixed rod 25 and thereafter round the draught roller 28 and the left-hand portion of the rod 25.  The filament during its passage from the right-hand to the left-hand portions of the rod 25 passes round the two short vertical pins 31 and 32 projecting from the central portion of the rod.  The filament may be stretched in two stages by means of apparatus of the type shown in Fig. 3, but in which the filament passes from a first to a second draught roller coaxial and contiguous with the first draught roller, but having a somewhat larger diameter and rotating at a higher peripheral speed, the fixed rod being of sufficient length to permit of the filament travelling in helical loops round both the second draught roller and a third portion of the fixed rod.  Instead of being capable of revolving independently of one another, the feed and the one or two draught rollers may be in the form of a single stepped roller, the first draught portion of the roller being of greater diameter than the feed portion and the second draught portion being of greater diameter than the first when the filament is drawn in two stages.  In the latter case also the feed roller portion may be detachably mounted on the remainder of the roller so that a feed roller portion may be substituted by another of different diameter.  An inclined fixed rod with projections, of the type shown in Fig. 3, co-operates with the stepped roller to cause the filament to advance as a helix round each portion of the stepped roller.  The filaments may also be of polyamino-undecanoic acid or polyethylene terephthalate.