GB849412A - Improved method and an apparatus for hot drawing artificial threads - Google Patents

Abstract

An apparatus for hot drawing artificial threads consisting of linear polycondensation products, especially highly polymeric polymethylene terephthalates, comprises a feed roll, a draw roll driven at a higher peripheral speed than the feed roll, a fixed snubbing pin or drum provided with heating means round which pin or drum the thread passes in one turn in its path of travel <PICT:0849412/IV(a)/1> <PICT:0849412/IV(a)/2> <PICT:0849412/IV(a)/3> <PICT:0849412/IV(a)/4> from the feed roll to the draw roll, the pin or drum being longitudinally split into two sections each made of a material having high thermal conductivity and the sections being at least partially spaced apart by a layer of air or of a solid heat insulating material, one of the sections being so disposed with respect to the feed roll that the travelling thread passes over and in contact with it before passing over and in contact with the other section and being maintained at a temperature which is not as high as that of the other section. As shown in Fig. 1, thread 2 is supplied over thread brake 1 to a driven feed roll 3 associated with rotatable pressure roll 4 and traversing thread guide 6. From supply roll 3 the thread passes in one turn round the snubbing pin or drum 7 and then in a number of turns round draw roll 8 and its associated guide roll 9. The pin 7 comprises a pair of segments 10 and 11 (Figs. 1 and 2) of heat conducting material spaced apart by small pins 12. Segment-shaped recesses 13 and 14 (Fig. 2) are provided in the boundary surfaces of segments 10 and 11 facing each other, the recesses serving as a socket for a plug 15 consisting of two segment-shaped portions 16 and 17 of which 16 consists of a material which is a good conductor of heat and 17 consists of a material which is poor conductor of heat. Plug 15 may be turned by means of a pin wrench fitting the bores 18. In the position shown in Fig. 2 the plug portion 16 forms a head conducting connection between the segments 10 and 11. If the plug 15 is turned until the boundary surface between the two segments 16 and 17 coincides with the two flat surfaces of the segments 10 and 11 the conducting connection between the segments 10 and 11 via the plug 15 is severed. Heat transfer from segment 10 to segment 11 may therefore be regulated by turning the plug 15. In the segment 10 a bore 19 running in longitudinal direction is provided in which an electric heating body 20 fits and which is connected to a tube 22 by means of a hollow support 21, the tube 22 being fixed to the frame of the drawing machine. The heating body is supplied with electric current by the leads 23 and 24. The segments 10 and 11 are covered by mantles 25 and 26 respectively of chromiumplated steel, which mantles do not touch each other. To prevent heat radiation an asbestos plate 27 is attached to the front of the pin 7 by means of a U-shaped bracket 28 of which the legs 29 fit into openings 30 in the segment 10. The thread 2 travels first over the surface of the mantle 26 of the lower segment 11 which may for example maintain the mantle at a temperature of 95 DEG C. After leaving the surface of the mantle 26 the thread passes over the surface of the mantle 25 which may for example be maintained at 145 DEG C. As shown in Fig. 3, the segment 10 is hollow so that it may be heated by means of a liquid or vaporous heating medium and the segment 11 is of smaller radius than the segment 10. Two strips of asbestos 33 are provided to reduce heat losses. As shown in Fig. 4, the temperature of the running-on section 11 is not adjustable relatively to that of section 10 and section 11 is separated from section 10 by an air space 34 and a gap 35 extending from one end face of the snubbing pin to the other. The invention renders the provision of a heating plate between the snubbing pin and the draw roll unnecessary.