Patent Publication Number: US-6216433-B1

Title: Flyer drafting arrangement having a condensing zone

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This application claims the priority of German patent application no. 199 02 194.5, filed in Germany on Jan. 21, 1999, the disclosure of which is expressly incorporated by reference herein. 
     The present invention relates to a flyer drafting arrangement having a condensing zone, arranged downstream of drafting rollers and bordered by a nipping point, for condensing a drafted fiber strand. 
     A flyer drafting arrangement is prior art in European published patent 455 190. Here it is disclosed that the drafted fiber strand exiting from the front roller pair of the flyer drafting arrangement is wider than it is high and therefore is laterally bundled in a condensing zone downstream of the flyer drafting rollers, so that the spinning triangle, to which the twist from the flyer spindle is retroactive, becomes narrower. A mechanical sliver condenser is provided in the condensing zone, with a delivery roller pair arranged downstream of the mechanical sliver condenser, and to which the twist from the flyer spindle is retroactive. 
     It has been shown in practice that such mechanical sliver condensers are not entirely satisfactory and that the condensed fibers spread out again before reaching the nipping point after they have left the sliver condenser. Furthermore, it has been shown that sliver condensers always result in a disimprovement in the evenness of the fiber strand. 
     It is an object of the present invention to create a condensing zone in which the fiber strand drafted in a flyer drafting arrangement is rounded in a satisfactory way so that the condensing effect is not lost. 
     This object has been achieved in accordance with the present invention in that a pneumatic condensing device is arranged at the condensing zone. 
     The present invention is based primarily on the knowledge that a pneumatic condensing device not only laterally bundles the drafted fiber strand, but also that it rolls the outer fibers additionally around the core strand, so that the condensing effect is maintained up to the nipping point. The drafted fiber strand is simultaneously rounded to a great extent, so that the twist applied subsequently by the flyer spindle is more even than is the case with the known mechanical sliver condenser. 
     The desired improvement attained in the condensing zone, arranged downstream of the flyer drafting rollers, is maintained until the ring spinning machine, at which the flyer roving is now more easily drafted. Due to the more even twist of the flyer roving, the twist in the subsequent ring yarn is also significantly more even. 
     The condensing zone is particularly simply designed when the condensing device comprises a suction device. The suction device can have a suction slit extending essentially in transport direction of the fiber strand, which suction slit is covered by an air-permeable transporting surface which transports the fiber strand. The width of the suction slit determines to a great extent the condensing effect, while the air-permeable transport surface ensures to a great extent a homogenous effect of the pneumatic condensing. 
     The condensing effect can be particularly great when the suction slit extends to the nipping point. This effectively prevents the condensed fiber strand from spreading out again before reaching the nipping point. 
     The transporting surface can have various designs. It is contemplated to form the transport surface by at least one guiding apron or to apply a sieve roller. The air-permeable effective width of the transport surface should be wider than that of the suction slit, which in turn should be wider than the width of the condensed fiber strand. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partly sectional side view of a schematically shown flyer drafting arrangement having a pneumatic condensing device arranged downstream thereof, constructed according to a preferred embodiment of the present invention; 
     FIG. 2 is a view in the direction of the arrow II of FIG. 1 onto the condensing device of two adjacent spinning stations; 
     FIG. 3 is a view similar to FIG. 1 having a different embodiment of a condensing device; 
     FIG. 4 is a view in the direction of the arrow IV of Figure III onto the condensing device; and 
     FIG. 5 is a view similar to FIGS. 1 and 3 onto a condensing device comprising a sieve roller. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The flyer drafting arrangement  1  shown in FIG. 1 comprises in a known way an entry roller pair  2 , an apron roller pair  3  as well as a front roller pair  4 , which forms a front nipping line  5 . In the flyer drafting arrangement  1 , a drafter sliver  6  is drafted in transport direction A to the desired degree of fineness and transported from the front roller pair  4  as a drafted fiber strand  7 , see also FIG.  2 . 
     Due to the large mass of the sliver  6 , the drafted fiber strand  7  has, downstream of the front nipping line  5 , a width which is significantly wider than its height. If the fiber strand  7  were twisted in such a state, a roving with very uneven twist distribution would arise. This uneven twist distribution would be carried over into the subsequent ring yarn. For this reason, a so-called condensing zone  8  is arranged downstream of the flyer drafting arrangement  1 , in which the drafted fiber strand  7  is held twist-free, but condensed by lateral bundling and rounding. 
     According to the present invention, the condensing zone  8  comprises a pneumatic condensing device  9 , which ensures that the condensing effect is maintained to the nipping point  10  which borders the condensing zone  8  on its exit side. The nipping point  10  forms then a twist block in relation to a flyer spindle  11  arranged downstream, to which the condensed fiber strand  19  is fed in delivery direction B. 
     The pneumatic condensing device  9  has a suction device  12 , which comprises a hollow profile  13 , which extends over a plurality of spinning stations  14 , 15 , . . . for example a machine section. The outer contour of the hollow profile  13  comprises, on the side facing the fiber strand  7 , per spinning station  14 , 15  a suction slit  16 , over which a guiding apron  17  slides. The guiding apron  17  is air-permeable as a result of a perforation, and forms a transport surface which slides over the hollow profile  13 , which transport surface transports the condensed fiber strand  7  through the condensing zone  8 . 
     The respective suction slit  16  is wider than the condensed fiber strand  19  and has a length which extends to the nipping point  10 . The suction slit  16  can extend inclined at a very slight angle to the transport direction A, so that the fiber strand  7  is imparted a slight false twist during condensing. 
     In the case of the guiding apron  17 , a thin closely woven material is preferred, which is made of, for example, plastic, so that its edges can be strengthed by means of welding. The effective width of the perforation of the guiding apron  17  is in any case so large that the entire suction slit  16  is covered. 
     Each hollow profile  13  comprises at least one suction connection  18 , for example one per machine section. A suction fan can hereby be arranged at each suction connection  18 . 
     The nipping point  10  is formed by a nipping roller  20 , which presses the guiding apron  17  and the fiber strand  7  against the sliding surface of the hollow profile  13  and at the same time drives the guiding apron  17 . The nipping roller  20  is in. turn driven by means of a transfer roller  21  by the front roller pair  4 . The transfer roller  21  can be coupled with the nipping roller  20  by means of intermediate wheels in such a way that the speed of the fiber strand  7  at the nipping point  10  is somewhat larger than at the front nipping line  5 . 
     In the following embodiments to be described, the same components, which are identical to those components shown in FIGS. 1 and 2, are provided with the same reference numbers, so that a repeat description can be omitted. 
     In the embodiment according to FIGS. 3 and 4, a delivery roller pair  22  is arranged downstream of the flyer drafting arrangement  1 , which delivery roller pair  22  comprises a driven bottom roller  23  extending in machine longitudinal direction, as well as a top roller  24 . The delivery roller pair  22  with its nipping point  10  borders the condensing zone  8 , arranged downstream of the flyer drafting arrangement  1 , on its exit side. Here again a pneumatic condensing device  9  is arranged at the condensing zone  8 . 
     The top roller  24  is looped by a perforated guiding apron  25  and drives same. The top roller  24  is in turn driven by the bottom roller  23  by means of friction. The guiding apron  25  extends from the front roller pair  4  over the entire condensing device  9  and slides over a sliding surface of a suction box  26 , which again comprises a suction slit  27  facing the fiber strand  7  and extending essentially in transport direction A. This suction slit  27 , however, cannot extend as far as the nipping point  10 . The suction box  26  has a suction connection  28 . 
     As can be seen from FIG. 4, the effective width c of the perforation of the guiding apron  25  is wider than the width of the suction slit  27 , so that a very homogenous suction airstream is generated. 
     In the embodiment according to FIG. 5 the condensing zone  8  comprises a pneumatic condensing device  9 , which comprises a sieve roller  29 . The diameter of the sieve roller  29  is significantly larger than the individual diameters of the entry roller pair  2 , the apron roller pair  3  and the front roller pair  4  of the flyer drafting arrangement  1 . 
     At a relatively large distance from the front nipping line  5 , the condensing zone  8  is bordered by a relatively small nipping roller  30 , on its exit side, which nipping roller  30  lightly presses the fiber strand  7  to the surface of the sieve roller  29  and defines a nipping point  10 , to which the twist, applied by the flyer spindle  11 , is retroactive. 
     In the inside of the sieve roller  29  a suction slit  31  is located, which again extends essentially in transport direction A. The sieve roller  29  is supported on a suction tube  32  in a way not shown, on which an adjustable suction insert  33  is applied, which determines the suction slit  31 . 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.